Tuesdays 10:30 - 11:30 | Fridays 11:30 - 12:30
Showing votes from 2023-12-05 11:30 to 2023-12-08 12:30 | Next meeting is Tuesday Oct 29th, 10:30 am.
Inflation, a period of exponential expansion in the early Universe, is considered an important part of the standard $\Lambda$CDM cosmological model, and plays a crucial role in explaining a wide range of current observations. The standard inflationary model predicts a primordial spectrum of fluctuations that is nearly scale-independent, fitting remarkably well the latest observational data. Nevertheless, there is an ongoing discussion surrounding the transition from an initial homogeneous and isotropic quantum state, characterizing the matter fields during inflation, to a classical inhomogeneous/anisotropic one, which gives rise to large-scale structure in the Universe. To tackle this issue, in the present work we explore an inflationary scenario where quantum ``collapse'' (or reduction) occurs naturally during the evolution of the system; this model is inspired in the so called Continuous Spontaneous Localization (CSL) model. Our present work builds upon previous results by considering the primordial power spectrum up to the second order in the Hubble Flow Functions, where we perform an estimation of the model free parameters. By validating the predictions of the model against observational data, we investigate whether this second-order calculation can explain the slight departure from the power law observed in the scalar spectral running index. We hope this research contributes to the understanding of the quantum-to-classical transition and its implications for cosmology.
For the first time we analyse gravitational-wave strain data using waveforms constructed from strong gravity simulations of cosmic string loops collapsing to Schwarzschild black holes; a previously unconsidered source. Since the expected signal is dominated by a black-hole ringdown, it can mimic the observed gravitational waves from high-mass binary black hole mergers. To illustrate this, we consider GW190521, a short duration gravitational-wave event observed in the third LIGO--Virgo--KAGRA observing run. We show that describing this event as a collapsing cosmic string loop is favoured over previous cosmic string analyses by an approximate log Bayes factor of $22$. The binary black hole hypothesis is still preferred, mostly because the cosmic string remnant is non-spinning. It remains an open question whether a spinning remnant could form from loops with angular momentum, but if possible, it would likely bring into contention the binary black hole preference. Finally, we suggest that searches for ringdown-only waveforms would be a viable approach for identifying collapsing cosmic string events. This work opens up an important new direction for the cosmic-string and gravitational-wave communities.
Cosmological parameters can be measured by comparing peculiar velocities with those predicted from a galaxy density field. Previous work has tested the accuracy of this approach with N-body simulations, but generally on idealised mock galaxy surveys. However, systematic biases may arise solely due to survey selection effects such as flux-limited samples, edge-effects, and complications due to the obscuration of the Galactic plane. In this work, we explore the impact of each of these effects independently and simultaneously, using the semi-analytic models from numerical simulations to generate mock catalogues that mimic the 2M++ density field. We find the reconstruction and analysis methods used for our 2M++ mocks produce a value of fsigma_8 that is biased high by a factor 1.04 \pm 0.01 compared to the true value. Moreover, a cosmic volume matching that of 2M++ has a cosmic variance uncertainty in fsigma_8 of ~5%. The systematic bias is a function of distance: it is unbiased close to the origin but is biased slightly high for distances in the range 100-180 Mpc/h. Correcting for this small bias, we find the linear fsigma_8 = 0.362 \pm 0.023. The predicted peculiar velocities from 2M++ have an error of 170 km/s that slowly increases with distance, exceeding 200 km/s only at distances of 180-200 Mpc/h. Finally, the residual bulk flow speeds found in previous work are shown to be not in conflict with those expected in the LCDM model.
Dark matter may consist of axion-like particles (ALPs). When polarized electromagnetic radiation passes through the dark-matter media, interaction with background ALPs affects the polarization of photons. The condensate of axionic dark matter experiences periodic oscillations, and the period of the oscillations is of order of years for ultra-light dark matter. This would result in observable periodic changes in the polarization plane, determined by the phases of the ALP field at the Earth and at the source. In this paper, we use recent polarimetric observations of the HL Tauri protoplanetary disk performed in different years to demonstrate the lack of changes of polarization angles, and hence to constrain masses and photon couplings of the hypothetical axion-like ultralight dark matter.
Convincing evidence of a stochastic gravitational wave background has been found by the NANOGrav collaboration in the 15-Year data set. From this signal, we can evaluate the possibility of its source being from the early universe through the tensor perturbations induced by a massive spin-2 graviton field. We consider a time dependent model of the minimal theory of massive gravity, and find values of the graviton mass, mass cutoff time, and Hubble rate of inflation that amplify the energy spectra of primordial gravitational waves sufficiently to reproduce the signal from the NANOGrav data within 1-3 standard deviation. However, a suppression mechanism for high frequency modes must be introduced to conservatively obey the big bang nucleosynthesis (BBN) bound. While there are regions of the parameter space that reproduces the signal, it remains a challenge to simultaneously respect the BBN and cosmic microwave background (CMB) bounds without making the graviton mass cutoff time too deep into the matter dominated era.
This paper explores the dark energy phenomenon within the context of $f(R,L_m)$ gravity theory. Two specific non-linear $f (R, L_m)$ models are considered: $f(R,L_m)=\frac{R}{2}+L_m^\alpha$ and $f(R,L_m)=\frac{R}{2}+(1+\alpha R)L_m$, where the parameter $\alpha$ is free. Here, we adopt a parametrization form for the Hubble parameter in terms of redshift $z$ as $H(z)=H_0 \left[A(1+z)^3+B+\epsilon \log(1+z)\right]^\frac{1}{2}$, which allows for deviations from the standard $\Lambda$CDM model at both low and high redshifts. We then incorporate the Hubble parameter solution into the Friedmann equations for both models. We employ Bayesian analysis to estimate the constraints on the free parameters $H_0$, $A$, $B$, and $\epsilon$ using the Hubble measurements and the Pantheon dataset. Further, we investigate the evolution of key cosmological quantities, such as the deceleration parameter, energy density, pressure, EoS parameter, and energy conditions. The evolution of the deceleration parameter reveals a significant transition from a decelerating phase to an accelerating phase in the Universe. The EoS parameter exhibits quintessence-like behavior for both non-linear $f (R, L_m)$ models.
Gravitational wave observations of binary black holes have revealed unexpected structure in the black hole mass distribution. Previous studies of the mass distribution employ physically-motivated phenomenological models and infer the parameters that directly control the features of the mass distribution that are allowed in their model, associating the constraints on those parameters with their physical motivations. In this work, we take an alternative approach in which we introduce a model parameterizing the underlying stellar and core-collapse physics and obtaining the remnant black hole distribution as a derived byproduct. In doing so, we directly constrain the stellar physics necessary to explain the astrophysical distribution of black hole properties under a given model. We apply this approach to modeling the mapping between stellar core mass and remnant black hole mass, including the effects of mass loss due to the pulsational pair instability supernova (PPISN) process, which has been proposed as an explanation for the observed excess of black holes at $\sim 35 M_\odot$. Placing constraints on the nuclear reaction rates necessary to explain the PPISN parameters, we conclude that the peak observed at $\sim 35 M_\odot$ is highly unlikely to be a signature from the PPISN process. This procedure can be applied to modeling any physical process that underlies the astrophysical mass distribution. Allowing the parameters of the core-remnant mass relationship to evolve with redshift permits correlated and physically reasonable changes in the location, shape, and amplitude of features in the mass function. We find that the current data are consistent with no redshift evolution in the core-remnant mass relationship, but ultimately place only weak constraints on the change of these parameters.
We study the dynamics of the quintom dark energy model using state-of-the-art cosmological observations. The set of equations has been converted into an autonomous system using suitable transformations of the variables. We have discussed the fixed points of the model and the general phase-space behavior, in particular, in finding the existence of the tracker solutions for this model. The observations suggest that at late times the phantom field should dominate the dark energy sector with an approximately 15% share to the quintessence counterpart, and with both fields tracking the background at early times. A Bayesian model comparison with LambdaCDM has also been done by computing the Bayes factor and a positive preference has been obtained for the quintom model. Although not fully resolved, the Hubble tension can be reduced to 2.6{\sigma} when compared with the value of H0 reported in [1] and to 1.6{\sigma} when compared with that of [2].
The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the $S_8$ tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of $\sigma_8$ parameter, in this paper, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS $w_{\rm dm}$ (referred as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, $\Lambda$WDM, and $\Lambda$CDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background (CMB), baryon acoustic oscillations (BAO), the Pantheon compilation, as well as a prior on $H_0$ (i.e., $H_0=73.04\pm1.04$, based on the latest local measurement by Riess et al.) and a Gaussianized prior on $S_8$ (i.e., $S_8=0.766\pm0.017$, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to $\sim$ 1.4$\sigma$, it still exacerbate the $S_8$ tension to a level similar to that of the axion-like EDE model.
Recent gravitational wave (GW) observations of binary black hole (BH) mergers and the stochastic GW background have triggered renewed interest in primordial black holes (PBHs) in the stellar-mass ($\sim 10 - 100\ \rm M_\odot$) and supermassive regimes ($\sim 10^7 - 10^{11}\ \rm M_\odot$). Although only a small fraction ($\lesssim 1\%$) of dark matter (DM) in the form of PBHs is required to explain such observations, these PBHs may play important roles in early structure/star/galaxy formation. In this chapter, we combine semi-analytical analysis and cosmological simulations to explore the possible impact of PBHs on the formation of the first stars and galaxies, taking into account two (competing) effects of PBHs: acceleration of structure formation and gas heating by BH accretion feedback. We find that the impact of stellar-mass PBHs (allowed by existing observational constraints) on primordial star formation is likely minor, although they do alter the properties of the first star-forming halos/clouds and can potentially trigger the formation of massive BHs, while supermassive PBHs serve as seeds of massive structures that can explain the apparent overabundance of massive galaxies in recent observations. Our tentative models and results call for future studies with improved modeling of the interactions between PBHs, particle DM, and baryons to better understand the impact of PBHs on early star/galaxy/structure formation and their imprints in high-redshift observations.
After more than five years of development, we present a new version of Dark Sage, a semi-analytic model (SAM) of galaxy formation that breaks the mould for models of its kind. Included among the major changes is an overhauled treatment of stellar feedback that is derived from energy conservation, operates on local scales, affects gas gradually over time rather than instantaneously, and predicts a mass-loading factor for every galaxy, which is a first for a SAM. Building on the model's resolved angular-momentum structure of galaxies, we now consider the heating of stellar discs, delivering predictions for disc structure both radially and vertically, another SAM first. We add a further dimension to stellar discs by tracking the distribution of stellar ages in each annulus. Each annulus--age bin has its own velocity dispersion and metallicity evolved in the model. This allows Dark Sage to make structural predictions for galaxies that previously only hydrodynamic simulations could. We present the model as run on the merger trees of the highest-resolution gravity-only simulation of the MillenniumTNG suite. Despite its additional complexity relative to other SAMs, Dark Sage only has three free parameters, the least of any SAM, which we calibrate exclusively against the cosmic star formation history and the $z=0$ stellar and HI mass functions using a particle-swarm optimisation method. The Dark Sage codebase, written in C and Python, is publicly available at https://github.com/arhstevens/DarkSage
We report the discovery of a radio relic in the northeastern periphery of the cluster Abell 2108 (A2108). A2108 is a part of the uGMRT LOw-MAss Galaxy Cluster Survey (GLOMACS), where our main aim is to search for diffuse radio emission signatures in very sparsely explored low-mass galaxy clusters using uGMRT band-3 (central frequency 400 MHz). We used our uGMRT band-3 data along with the existing archival band-3 uGMRT data to improve image sensitivity. Along with the previously reported southwestern relic, the discovery of the new relic makes A2108 one of the few low-mass clusters hosting double relics. The new relic spans over a region of 610 kpc $\times$ 310 kpc and, interestingly, differs considerably in size and morphology from the other relic. With XMM-Newton science archive data, we also report the tentative detection of a mildly supersonic shock of Mach number $\mathcal{M}_\mathrm{SB}=1.42$ and $\mathcal{M}_\mathrm{T} = 1.43$ from the surface brightness and temperature discontinuities, respectively near this newly found relic. Both the relics in A2108 are found to be significantly under-luminous compared to other double relic systems in the mass-luminosity plane. Though mild supersonic shocks resulting from an off-axis merger could have influenced their origin, we hypothesize that further local environments have played a crucial role in shaping their morphology.
Cosmological studies have now entered Stage IV according to the Dark Energy Task Force prescription, thanks to new missions (Euclid, Rubin Observatory, SRG/eROSITA) that are expected to provide the required ultimate accuracy in the dark energy (DE) equation of state (EoS). However, none of these projects have the power to systematically unveil the galaxy cluster population at $z>1$. There therefore remains the need for an ATHENA-like mission to run independent cosmological investigations and scrutinise the consistency between the results from the $0<z<1$ and $1<z<2$ epochs. We study the constraints on the DE EoS and on primordial non-Gaussanities for typical X-ray cluster surveys executed by ATHENA. We consider two survey designs: 50 deg$^2$ at 80ks (survey A) and 200 deg$^2$ at 20ks (survey B). We analytically derive cluster counts in a space of observable properties, and predict the cosmological potential of the corresponding samples with a Fisher analysis. The achieved depth allows us to unveil the halo mass function down to the group scale out to $z=2$. We predict the detection of thousands of clusters down to a few 10$^{13} h^{-1} M_{\odot}$, in particular 940 and 1400 clusters for surveys A and B, respectively, at $z>1$. Such samples will allow a detailed modelling of the evolution of cluster physics along with a standalone cosmological analysis. Our results suggest that survey B has the optimal design as it provides greater statistics. Remarkably, high-$z$ clusters, despite representing 15% or less of the full samples, allow a significant reduction of the uncertainty on the cosmological parameters: $\Delta w_a$ is reduced by a factor of 2.3 and $\Delta f_{NL}^{loc}$ by a factor of 3. Inventorying the high-$z$ X-ray cluster population can play a crucial role in ensuring overall cosmological consistency. This will be the major aim of future new-generation ATHENA-like missions.
During the Epoch of Reionization (EoR), the ultraviolet radiation from the first stars and galaxies ionised the neutral hydrogen of the intergalactic medium, which can emit radiation through its 21 cm hyperfine transition. This 21 cm signal is a direct probe of the first light sources in the early Universe. Measuring the 21 cm power spectrum is a key science goal for the future Square Kilometre Array (SKA), however, observing and interpreting it is a challenging task. Another high-potential probe of the EoR is the patchy kinetic Sunyaev-Zel'dovich effect (pkSZ), observed as a foreground to the primary cosmic microwave background temperature anisotropies on small scales. Despite recent promising measurements by ground-based telescopes, placing constraints on reionization from pkSZ observations is a non-trivial task, subject to strong model dependence. In this work, we propose to alleviate the difficulties in observing and interpreting the 21 cm and pkSZ power spectra by combining them. With a simple yet effective parametric model that establishes a formal connection between them, we are able to jointly fit mock 21 cm and pkSZ data points. We confirm that these two observables provide complementary information on reionization, leading to significantly improved constraints when combined. We demonstrate that with as few as two measurements of the 21 cm power spectrum with 100 hours of observations with the SKA, as well as a single $\ell=3000$ pkSZ data point, we can reconstruct the reionization history of the Universe and its morphology. We find that the reionization global history (morphology) is better constrained with two 21 cm measurements at different redshifts (scales). Therefore, a combined analysis of the two probes will give access to tighter constraints on cosmic reionization even in the early stages of 21 cm detections.
We develop the Brans-Dicke theory of gravity in the context of varying constants of Nature. Using the unimodular formalism of General Relativity, we create a platform to provide physical relational times giving the evolution of physical constants. We therefore review the ideas and experiments behind varying constants, mostly focusing on the speed of light and the gravitational constant. Then, we apply this idea to the energy conservation in cosmology, illustrating the arising patterns. Motivated by a varying gravitational constant resulting from Mach's principle, we develop the unimodular formalism of varying constants in the Brans-Dicke theory. Doing so, we obtain several original results, some of which can be compared with phenomenological observation. Finally, we suggest how a varying Brans-Dicke parameter could be linked to the Cosmological Constant problem.
Neutrinos are believed to be the most abundant fermions in the Universe, but their masses are unknown, except for being non-zero but much smaller than other fermions. Cosmological relic neutrinos could also have non-zero chemical potentials (or asymmetries). We develop a fast neutrino-involved N-body simulation code to include both neutrino mass and asymmetry effects. Using it, we investigate the neutrino effects on the matter pairwise velocity, which itself is an interesting probe of cosmology. We find that for light-halo ($[10^{11},10^{13}]\ M_\odot$) mean pairwise velocity, in the transition range ($[4,15]\ \mathrm{Mpc}$), the effects of neutrino masses overwhelm the effects of neutrino asymmetries, while in the two-halo-group range ($[25,50]\ \mathrm{Mpc}$), for both light and heavy haloes ($[10^{13},10^{15}]\ M_\odot$), the effects of neutrino asymmetries dominate, making it possible to disentangle the two effects. We provide fitting formulae to quantify the effects of neutrino mass and asymmetry on halo-halo pairwise velocities.
Extremely large telescopes (ELTs) are considered worldwide to be one of the highest priorities in ground-based astronomy. The European Southern Observatory (ESO) is developing an ELT that will have a 39 m main mirror and will be the largest visible and infrared light telescope in the world. The ELT will be equipped with a lineup of cutting-edge instruments, designed to cover a wide range of scientific possibilities. The leap forwards with the ELT can lead to a paradigm shift in our perception of the Universe, much as Galileo's telescope did 400 years ago. We illustrate here the various components of the ELT, including the dome and main structure, the five mirrors, and the telescope systems. We then describe the ELT instrumentation and some of the astronomical topics it will address. We then conclude by examining the synergies with other astronomical facilities.
We develop a method for accurately calculating vacuum decay rates beyond the thin-wall regime in a pure scalar field theory at the one-loop level of the effective action. It accounts for radiative effects resulting from quantum corrections to the classical bounce, including gradient effects stemming from the inhomogeneity of the bounce background. To achieve this, it is necessary to compute not only the functional determinant of the fluctuation operator in the background of the classical bounce but also its functional derivative evaluated at the classical bounce. The former is efficiently calculated using the Gel'fand-Yaglom method. We illustrate how the latter can also be calculated with the same method, combined with a computation of various Green's functions.
We estimate the redshift-dependent, anisotropic clustering signal in DESI's Year 1 Survey created by tidal alignments of Luminous Red Galaxies (LRGs) and a selection-induced galaxy orientation bias. To this end, we measured the correlation between LRG shapes and the tidal field with DESI's Year 1 redshifts, as traced by LRGs and Emission-Line Galaxies (ELGs). We also estimate the galaxy orientation bias of LRGs caused by DESI's aperture-based selection, and find it to increase by a factor of seven between redshifts 0.4 - 1.1 due to redder, fainter galaxies falling closer to DESI's imaging selection cuts. These effects combine to dampen measurements of the quadrupole of the correlation function caused by structure growth on scales of 10 - 80 Mpc/h by about 0.15% for low redshifts (0.4<z<0.6) and 0.8% for high (0.8<z<1.1). We provide estimates of the quadrupole signal created by intrinsic alignments that can be used to correct this effect, which is necessary to meet DESI's forecasted precision on measuring the growth rate of structure. While imaging quality varies across DESI's footprint, we find no significant difference in this effect between imaging regions in the Legacy Imaging Survey.
The large scale geometry of the late Universe can be decomposed as R$\times {\Sigma}_3$, where R stands for cosmic time and ${\Sigma}_3$ is the three dimensional spatial manifold. We conjecture that the spatial geometry of the Universe's spatial section ${\Sigma}_3$ conforms with the Thurston-Perelman theorem, according to which the geometry of $\Sigma_3$ is either one of the eight geometries from the Thurston geometrization conjecture, or a combination of Thurston geometries smoothly sewn together. We assume that topology of individual geometries plays no observational role, i.e. the size of individual geometries is much larger than the Hubble radius today. We investigate the dynamics of each of the individual geometries by making use of the simplifying assumption that our local Hubble patch consists of only one such geometry, which is approximately homogeneous on very large scales, but spatial isotropy is generally violated. Spatial anisotropies grow in time in decelerating universes, but they decay in accelerating universes. The thus-created anisotropy problem can be solved by a period of primordial inflation, akin to how the flatness problem is solved. Therefore, as regards Universe's large scale geometry, any of the Thurston's geometries should be considered on a par with Friedmann's geometries. We consider two observational methods that can be used to test our conjecture: one based on luminosity distance and one on angular diameter distance measurements, but leave for the future their detailed forecasting implementations.
Photometric redshifts are a key ingredient in the analysis and interpretation of large-scale structure (LSS) surveys. The accuracy and precision of these redshift estimates are directly linked to the constraining power of photometric surveys. It is hence necessary to define precision and accuracy requirements for the redshift calibration \revision{to not} infer biased results in the final analysis. For weak gravitational lensing of the LSS, the photometry culminates in the estimation of the source redshift distribution (SRD) in each of the tomographic bins used in the analysis. The focus has been on shifts of the mean of the SRDs and how well the calibration must be able to recover those. Since the estimated SRDs are usually given as a normalized histogram with corresponding errors, it would be advantageous to propagate these uncertainties accordingly to see whether the requirements of the given survey are indeed fulfilled. Here we propose the use of functional derivatives to calculate the sensitivity of the final observables, e.g. the lensing angular power spectrum, with respect to the SRD at a specific redshift. This allows the propagation of arbitrarily shaped small perturbations to the SRD, without having to run the whole analysis pipeline for each realization again. We apply our method to an EUCLID survey and demonstrate it with SRDs of the KV450 data set, recovering previous results. Lastly, we note that the moments of the SRD of order larger than two will probably not be relevant when propagating redshift uncertainties in cosmic shear analysis.
Observations of local star-forming galaxies (SFGs) show a tight correlation between their singly ionized carbon line luminosity ($L_{\rm [C_{II}]}$) and star formation rate (SFR), suggesting that $L_{\rm [C_{II}]}$ may be a useful SFR tracer for galaxies. Some other galaxy populations, however, are found to have lower $L_{\rm [C_{II}]}{}/{}\rm SFR$ than the local SFGs, including the infrared-luminous, starburst galaxies at low and high redshifts, as well as some moderately star-forming galaxies at the epoch of re-ionization (EoR). The origin of this `$\rm [C_{II}]$ deficit' is unclear. In this work, we study the $L_{\rm [C_{II}]}$-SFR relation of galaxies using a sample of $z=0-8$ galaxies with $M_*\approx10^7-5\times10^{11}\,M_\odot$ extracted from cosmological volume and zoom-in simulations from the Feedback in Realistic Environments (FIRE) project. We find a simple analytic expression for $L_{\rm [C_{II}]}$/SFR of galaxies in terms of the following parameters: mass fraction of $\rm [C_{II}]$-emitting gas ($f_{\rm [C_{II}]}$), gas metallicity ($Z_{\rm gas}$), gas density ($n_{\rm gas}$) and gas depletion time ($t_{\rm dep}{}={}M_{\rm gas}{}/{}\rm SFR$). We find two distinct physical regimes, where $t_{\rm dep}$ ($Z_{\rm gas}$) is the main driver of the $\rm [C_{II}]$ deficit in $\rm H_2$-rich ($\rm H_2$-poor) galaxies. The observed $\rm [C_{II}]$ deficit of IR-luminous galaxies and early EoR galaxies, corresponding to the two different regimes, is due to short gas depletion time and low gas metallicity, respectively. Our result indicates that $\rm [C_{II}]$ deficit is a common phenomenon of galaxies, and caution needs to be taken when applying a constant $L_{\rm [C_{II}]}$-to-SFR conversion factor derived from local SFGs to estimate cosmic SFR density at high redshifts and interpret data from upcoming $\rm [C_{II}]$ line intensity mapping experiments.
Large-scale cosmological simulations are an indispensable tool for modern cosmology. To enable model-space exploration, fast and accurate predictions are critical. In this paper, we show that the performance of such simulations can be further improved with time-stepping schemes that use input from cosmological perturbation theory. Specifically, we introduce a class of time-stepping schemes derived by matching the particle trajectories in a single leapfrog/Verlet drift-kick-drift step to those predicted by Lagrangian perturbation theory (LPT). As a corollary, these schemes exactly yield the analytic Zel'dovich solution in 1D in the pre-shell-crossing regime (i.e. before particle trajectories cross). One representative of this class is the popular FastPM scheme by Feng et al. 2016, which we take as our baseline. We then construct more powerful LPT-inspired integrators and show that they outperform FastPM and standard integrators in fast simulations in two and three dimensions with $\mathcal{O}(1 - 100)$ timesteps, requiring less steps to accurately reproduce the power spectrum and bispectrum of the density field. Furthermore, we demonstrate analytically and numerically that, for any integrator, convergence is limited in the post-shell-crossing regime (to order 3/2 for planar wave collapse), owing to the lacking regularity of the acceleration field, which makes the use of high-order integrators in this regime futile. Also, we study the impact of the timestep spacing and of a decaying mode present in the initial conditions. Importantly, we find that symplecticity of the integrator plays a minor role for fast approximate simulations with a small number of timesteps.
It is known that the single-field inflation with a transient ultra-slow-roll phase can produce a large curvature perturbation at small scales for the formation of primordial black holes. In our previous work, we have considered quantum loop corrections to the curvature perturbation and found that the growth of these small-scale modes would affect the curvature perturbation at large scales probed by cosmic microwave background observation. In this work, we will further derive the constraints on the growing modes in the transition between the slow-roll and the ultra-slow-roll phases under the effect of the loop corrections. Our results would help clarify the recent controversy on whether or not the primordial-black-hole formation from the single-field inflation is ruled out at one-loop level.
In the presence of (relatively) long-range forces, structures can form even during the radiation dominated era, leading to compact objects, such as Fermi balls or primordial black holes (PBHs), which can account for all or part of dark matter. We present a detailed analysis of a model in which fermions are produced from the inflaton decay developing some particle-antiparticle asymmetry. These fermions undergo clustering and structure formation driven by a Yukawa interaction. The same interaction provides a cooling channel for the dark halos via scalar radiation, leading to rapid collapse and the formation of a compact object. We discuss the criteria for the formation of either PBHs and Fermi balls. In the PBH formation regime, supermassive PBHs can seed the active galactic nuclei or quasars found at high redshift. Alternatively, Fermi balls can account for all of the cold dark matter, while evading microlensing constraints.
We study a simple axionlike model with a charged scalar $\phi$ and a double-charged scalar $\zeta$ of global $U(1)$ symmetry. A particular feature of our model is that a vacuum manifold is a torus knot. We consider a hierarchical symmetry-breaking scenario where $\zeta$ first condenses, giving rise to cosmic $\zeta$-strings, and the subsequent condensation of $\phi$ leads to domain-wall formation spanning the $\zeta$-strings. We find that the formation of the walls undergoes two different regimes depending on the magnitude of an explicit breaking term of the relative $U(1)$ between $\zeta$ and $\phi$. One is the weakly interacting regime where the walls are accompanied by another cosmic $\phi$ strings. The other is the strongly interacting regime where no additional strings appear. In both regimes, neither a $\zeta$-string, a $\phi$-string nor a wall alone is topological, but the composite of an appropriate number of strings and walls as a whole is topologically stable, characterized by the fundamental homotopy group of the torus knot. We confirm the formation and the structure of the string-wall system by first-principle cosmological two-dimensional simulations. We find stable string-wall composites at equilibrium, where the repulsive force between $\zeta$-strings and the tension of walls balances, and a novel reconnection of the string-wall composites.
Several modified gravity theories predict a possible time variation of the propagation speed of gravitational waves (GW) which could be tested with multimessenger astronomy. For this purpose we derive the relation between the redshift dependence of the propagation speed of GWs and the time delay between the detection of GWs and electromagnetic waves (EMWs) emitted by the same source. For theories with Einstein frame minimal matter-gravity coupling (EMC) the propagation speed of GWs can be jointly constrained by the time delay between GWs and EWs and the GW-EMW luminosity distance ratio, allowing to derive a consistency relation between these two observables. The event GW 170817 and its EM counterpart satisfy the consistency condition, confirming the EMC, and allow to set strong constraints on the time variation of the GWs speed.
In cluster cosmology, cluster masses are the main parameter of interest. They are needed to constrain cosmological parameters through the cluster number count. As the mass is not an observable, a scaling relation is needed to link cluster masses to the integrated Compton parameters Y, i.e. the Sunyaev-Zeldovich observable (SZ). Planck cosmological results obtained with cluster number counts are based on a scaling relation measured with clusters at low redshift ($z$<0.5) observed in SZ and X-ray. In the SZ Large Program (LPSZ) of the NIKA2 collaboration, the scaling relation will be obtained with a sample of 38 clusters at intermediate to high redshift ($0.5<z<0.9$) and observed at high angular resolution in both SZ and X-ray. Thanks to analytical simulation of LPSZ-like samples, we take into account the LPSZ selection function and correct for its effects. Besides, we show that white and correlated noises in the SZ maps do not affect the scaling relation estimation.
This paper investigates a hypothesis proposed in previous research relating neutron star (NS) mass and its dark matter (DM) accumulation. As DM accumulates, NS mass decreases, predicting lower NS masses toward the Galactic center. Due to limited NSs data near the galactic center, we examine NSs located within DM clumps. Using the CLUMPY code simulations, we determine the DM clumps distribution, with masses from 10 to $10^{8}$ $M_{\odot}$ and scales from $10^{-3}$ to 10 kpc. These clumps' DM exhibit a peak at the center, tapering toward the outskirts, resembling our Galaxy's DM distribution. We analyse these DM clumps' NS mass variations, considering diverse DM particle masses and galaxy types. We find relatively stable NS mass within 0.01 to 5 kpc from the clump center. This stability supports the initial hypothesis, particularly for NSs located beyond 0.01 kpc from the clump center, where NS mass reaches a plateau around 0.1 kpc. Nevertheless, NS mass near the clump's periphery reveals spatial dependence: NS position within DM clumps influences its mass in Milky Way-type galaxies. Moreover, this dependence varies with the DM model considered. In summary, our study investigates the proposed link between NS mass and DM accumulation by examining NSs within DM clumps. While NS mass remains stable at certain distances from the clump center, spatial dependencies arise near the clump's outer regions, contingent on the specific DM model.
Dark matter haloes form from small perturbations to the almost homogeneous density field of the early universe. Although it is known how large these initial perturbations must be to form haloes, it is rather poorly understood how to predict which particles will end up belonging to which halo. However, it is this process that determines the Lagrangian shape of protohaloes and is therefore essential to understand their mass, spin and formation history. Here, we present a machine-learning framework to learn how the protohalo regions of different haloes emerge from the initial density field. This involves one neural network to distinguish semantically which particles become part of any halo and a second neural network that groups these particles by halo membership into different instances. This instance segmentation is done through the Weinberger method, in which the network maps particles into a pseudo-space representation where different instances can be distinguished easily through a simple clustering algorithm. Our model reliably predicts the masses and Lagrangian shapes of haloes object-by-object, as well as summary statistics like the halo-mass function. We find that our model extracts information close to optimal by comparing it to the degree of agreement between two N-body simulations with slight differences in their initial conditions. We publish our model open-source and suggest that it can be used to inform analytical methods of structure formation by studying the effect of systematic manipulations of the initial conditions.
The flavor evolution of neutrinos in dense astrophysical sources, such as core-collapse supernovae or compact binary mergers, is non-linear due to the coherent forward scattering of neutrinos among themselves. Recent work in this context has been addressed to figure out whether flavor equipartition could be a generic flavor outcome of fast flavor conversion. We investigate the flavor conversion physics injecting random perturbations in the neutrino field in two simulation setups: 1. a spherically symmetric simulation shell without periodic boundaries, with angular distributions evolving dynamically thanks to non-forward scatterings of neutrinos with the background medium, and neutrino advection; 2. a periodic simulation shell, with angular distributions of neutrinos defined a priori and neutrino advection. We find that, independent of the exact initial flavor configuration and type of perturbations, flavor equipartition is generally achieved in the system with periodic boundaries; in this case, perturbations aid the diffusion of flavor structures to smaller and smaller scales. However, flavor equipartition is not a general outcome in the simulation shell without periodic boundaries, where the inhomogeneities induced perturbing the neutrino field affect the flavor evolution, but do not facilitate the diffusion of flavor waves. This work highlights the importance of the choice of the simulation boundary conditions in the exploration of fast flavor conversion physics.
AT 2019azh is a H+He tidal disruption event (TDE) with one of the most extensive ultraviolet and optical datasets available to date. We present our photometric and spectroscopic observations of this event starting several weeks before and out to approximately two years after g-band peak brightness and combine them with public photometric data. This extensive dataset robustly reveals a change in the light-curve slope and a bump in the rising light curve of a TDE for the first time, which may indicate more than one dominant emission mechanism contributing to the pre-peak light curve. We further confirm the relation seen in previous TDEs whereby the redder emission peaks later than the bluer emission. The post-peak bolometric light curve of AT 2019azh is better described by an exponential decline than by the canonical t^{-5/3} (and in fact any) power-law decline. We find a possible mid-infrared excess around peak optical luminosity, but cannot determine its origin. In addition, we provide the earliest measurements of the Halpha emission-line evolution and find no significant time delay between the peak of the V-band light curve and that of the Halpha luminosity. These results can be used to constrain future models of TDE line formation and emission mechanisms in general. More pre-peak 1-2 day cadence observations of TDEs are required to determine whether the characteristics observed here are common among TDEs. More importantly, detailed emission models are needed to fully exploit such observations for understanding the emission physics of TDEs.
We study the effects of the first nontrivial hexaquark, $d^*$(2380), on the equation of state of dense neutron star matter and investigate the consequences of its existence for neutron stars. The matter in the core regions of neutron stars is described using density-dependent relativistic mean-field theory. Our results show that within the parameter spaces examined in our paper, (i) the critical density at which the $d^*$ condensate emerges lies between 4 and 5 times the nuclear saturation density, (ii) $d^*$ hexaquarks are found to exist only in rather massive neutron stars, (iii) only relatively small fractions of the matter in the core of a massive neutron star may contain hexaquarks.
Microbursts are short duration intensifications in precipitating electron flux that are believed to be a significant contributor to electron losses in the magnetosphere. Microbursts have been observed in the form of bouncing electron packets, which offer a unique opportunity to study the properties of microbursts and their importance as a loss process. We present a collection of bouncing microbursts observed by the HILT instrument on SAMPEX from 1994-2004.We analyze the locations of the bouncing microbursts in L and MLT and find they align well with the properties of relativistic microbursts as a whole. We find that that the majority of bouncing microbursts observed by SAMPEX have scale sizes of 30km at the point of observation, or about 1500km when mapped to the equator.The time separation between the peaks of these bouncing microbursts is usually either half a bounce period or a whole bounce period.
Many polyatomic astrophysical plasmas are compressible and out of chemical and thermal equilibrium, and yet, due to Stokes' hypothesis, a means to carefully control the decay of compressible modes in these systems has largely been neglected. This is especially important for small-scale, turbulent dynamo processes, which are known to be sensitive to the effects of compression. To control the viscous properties of the compressible modes, we perform supersonic, visco-resistive dynamo simulations with additional bulk viscosity $\nu_{\rm bulk}$, deriving a new $\nu_{\rm bulk}$ Reynolds number $\rm{Re}_{\rm bulk}$, and viscous Prandtl number $\rm{P}\nu \equiv \rm{Re}_{\rm bulk} / \rm{Re}_{\rm shear}$, where $\rm{Re}_{\rm shear}$ is the shear viscosity Reynolds number. For $10^{-3} \leq \rm{P}\nu \leq \infty$, we explore a broad range of statistics critical to the dynamo problem, including the integral and spectral energy ratios, growth rates, and the magnetic $E_{\rm mag}(k)$ and kinetic $E_{\rm kin}(k)$ energy spectrum. We derive a general framework for decomposing $E_{\rm mag}$ growth rates into incompressible and compressible terms via orthogonal tensor decompositions of $\nabla\otimes\mathbf{v}$, where $\mathbf{v}$ is the fluid velocity. We find that compressible modes play a dual role, growing and decaying $E_{\rm mag}$, and that field-line stretching is the main driver of growth, even in supersonic dynamos. In the absence of $\nu_{\rm bulk}$, compressible modes pile up on small-scales, creating an apparent spectral bottleneck, which disappears for $\rm{P}\nu \approx 1$. As $\rm{P}\nu$ decreases, compressible modes are dissipated at increasingly larger scales, in turn suppressing incompressible modes through a coupling between viscosity operators. We emphasise the importance of further understanding the role of $\nu_{\rm bulk}$ in compressible astrophysical plasmas.
The discovery of gravitational waves (GWs) opens a new window for exploring the physics of the early universe. Identifying the source of GWs and their spectra today turn out to be the important tasks so as to assist the experimental detection of stochastic GWs. In this paper, we investigate the oscillations of the ultralight dark photon (ULDP) into GWs in the dark halo. Assuming dark matter is composed of the ULDP and there are primordial dark magnetic fields (PDMFs) arising from the axion inflation and/or the dark phase transition, then the ULDP can oscillate into the GW when it passes through an environment of PDMFs. We derive the local energy density of GWs in the galaxy cluster induced by the instaneous oscillation of ULDP in the PDMFs. These stochastic local GWs exhibit a pulse-like spectrum, with frequency depending on the mass of the ULDP, and can be detected in Pulsar Timing Arrays (PTAs) or future space-based interferometers. We also find that the low-frequency GW signal observed by the NANOGrav collaboration and other PTA experiments can be explained by the oscillation of the ULDP in the PDMFs in the early universe.
General-relativistic magneto-hydrodynamical (GRMHD) simulations of accreting black holes suggest that the accretion flows form toroidal structures embedded in a large scale component of magnetic field, which becomes organized on length-scales exceeding the gravitational radius of the central black hole. Magnetic field grows gradually until a Magnetically Arrested Disc (MAD) develops that diminishes or inhibits further accretion. We study an outflow that develops in the MAD state in 3D GRMHD simulations. We show that the outflow can be accelerated to relativistic velocities and persist over the course of our simulation. We compare the properties of the outflow from MAD discs with those launched by orbiting secondary at close orbit. The main difference is that the orbiting body launches a more coherent, quasiperiodic ultrafast outflow at lower velocities ($v<0.5c$) while the outflow launched in the MAD state (without the body) has a stochastic behaviour and has an approximately flat velocity distribution between lower and higher outflow velocities, $0.2c<v<0.3c$ and $v>0.5c$.
The mergers of two neutron stars are exceptional multi-messenger events that enable us to probe fundamental physics in one of the most extreme environments in the Universe. Multi-wavelength follow-up observations are essential in order to probe the physics of the outflows from and remnants of these neutron star mergers, both when detected as short gamma-ray bursts (GRBs) and as gravitational wave events. Rapid follow-up can provide localisations for targeted deep follow-up observations and, ideally, a distance measurement, which constrains for instance the energetics of the merger. A key outstanding question is the remnant's nature: with its expected mass and rapid spin, it could either be a black hole or a supramassive, likely highly magnetised neutron star (a magnetar). Both can power a GRB, but rapidly spinning magnetars are additionally predicted to emit coherent radio bursts following their formation and may constitute a small fraction of the progenitors of fast radio bursts. Black holes, by contrast, are not expected to emit coherent radio bursts in the time following the GRB itself. Here we present rapid follow-up observations of the short GRB 201006A using LOFAR. We have detected a 5.6$\sigma$, short, coherent radio flash at 144 MHz at 76.6 mins post-burst. This radio flash is 27 arcsec offset from the GRB location, which has a probability of occurring by chance of $\sim$0.5% (2.6$\sigma$) when accounting for measurement uncertainties. Despite the offset, we show that the probability of finding an unrelated transient within 40 arcsec of the GRB location is $<10^{-6}$ and conclude that this is likely to be the radio counterpart to GRB 201006A. The radio flash is tentatively (2.5$\sigma$) shown to be highly dispersed, allowing a distance estimate, corresponding to a redshift of $0.58\pm0.06$, that is in the range of typical short GRB distances. Using the estimated distance, the...
T Pyx is one of the most enigmatic recurrent novae, and it has been proposed as a potential Galactic type-Ia supernova progenitor. Using spatially-resolved data obtained with MUSE, we characterized the geometrical distribution of the material expelled in previous outbursts surrounding the white dwarf progenitor. We used a 3D model for the ejecta to determine the geometric distribution of the extended remnant. We have also calculated the nebular parallax distance ($d = 3.55 \pm 0.77$ kpc) based on the measured velocity and spatial shift of the 2011 bipolar ejecta. These findings confirm previous results, including data from the GAIA mission. The remnant of T Pyx can be described by a two-component model, consisting of a tilted ring at $i = 63.7$ deg, relative to its normal vector and by fast bipolar ejecta perpendicular to the plane of the equatorial ring. We find an upper limit for the bipolar outflow ejected mass in 2011 of the bipolar outflow of $M_{ej,b} < (3.0 \pm 1.0) \times 10^{-6}$ M$_{\odot}$, which is lower than previous estimates given in the literature. However, only a detailed physical study of the equatorial component could provide an accurate estimate of the total ejecta of the last outburst, a fundamental step to understand if T Pyx will end its life as a type-Ia supernova.
In this study, we delve into the observational implications of rotating Loop Quantum Black Holes (LQBHs) within an astrophysical framework. We employ semi-analytical General Relativistic Radiative Transfer (GRRT) computations to study the emission from the accretion flow around LQBHs. Our findings indicate that the increase of Loop Quantum Gravity (LQG) effects results in an enlargement of the rings from LQBHs, thereby causing a more circular polarization pattern in the shadow images. We make comparisons with the Event Horizon Telescope (EHT) observations of Sgr\,A$^*$ and M\,87$^*$, which enable us to determine an upper limit for the polymetric function $P$ in LQG. The upper limit for Sgr\,A$^*$ is $0.2$, while for M\,87$^*$ it is $0.07$. Both black holes exhibit a preference for a relatively high spin ($a\gtrsim0.5$ for Sgr\,A$^*$ and $0.5\lesssim a \lesssim 0.7$ for M\,87$^*$). The constraints for Sgr\,A$^*$ are based on black hole spin and ring diameter, whereas for M\,87$^*$, the constraints are further tightened by the polarimetric pattern. In essence, our simulations provide observational constraints on the effect of LQG in supermassive black holes (SMBH), providing the most consistent comparison with observation.
An explanation is proposed for the appearance of slowly drift shadow bursts in the dynamic spectrum of Jupiter against the background of decameter radio emission with a quasi-harmonic structure. Background radio emission is caused by hot ions with a loss cone type distribution function, which generate ion cyclotron waves due to the effect of double plasma resonance. A flow of hot ions with a distribution function of the Maxwell type is injected into the source region, fills the loss cone of generating ions and interrupts the generation of ion cyclotron waves due to the filling of the loss cone. The condition under which instability breaks down is obtained, and the optimal values of the parameters of the injected ions necessary for the occurrence of bursts in absorption are determined.
PSR J1048$-$5832 (B1046$-$58) is a Vela-like pulsar that has exhibited multiple glitch events. In this study, we analyze the timing data spanning nearly 16 years, acquired from both the Fermi Gamma-ray Space Telescope and the Parkes 64 m radio telescope. As a result, a total of five glitches are detected within this dataset. Among them, a previously unknown small glitch is newly found at MJD 56985(9) (November 24, 2014), which is also the smallest glitch recorded from this source so far. The increments of the spin frequency and its first derivative are $\Delta \nu \approx 2.2(3) \times 10^ {-8} $ Hz, and $\Delta \dot{\nu} \approx 3(2) \times 10^ {-15} $ s$^{-2}$, respectively. Significant changes in the integrated mean pulse profile are observed following two of the five glitch events, notably in the radio band. We discuss the influence of glitches on the pulsar's emission properties due to superfluid dynamics accompanied by crustquake, as well as the constraints on the equation of state.
Context: T CrB (NOVA CrB 1946) is a famous recurrent nova with a recurrence timescale of 80 years. Aims: We aim to estimate the colours, luminosity, and mass-accretion rate for T CrB (NOVA CrB 1946) during and after the superactive state. Methods and Results: We performed and analysed $UBV$ photometry of the recurrent nova T~CrB. For the hot component of T~CrB, we find average dereddened colours of $(U-B)_0 = -0.70 \pm 0.08$ and $(B-V)_0 = 0.23 \pm 0.06$, which correspond to an effective temperature of $9400 \pm 500$~K and an optical luminosity of $40-110~L_\odot$ during the superactive state (2016-2022). After the end of the superactive state, the hot component became significantly redder, $(U-B)_0 \approx -0.3$ and $(B-V)_0 \approx 0.6$ in August 2023, and its luminosity decreased markedly to $20-25$~$L_\odot$ in April-May 2023, and to $8-9~L_\odot$ in August 2023. The total mass accreted during the superactive state from 2014 to 2023 is $\sim 2 \times 10^{-7}$~M$_\odot$. This is a significant fraction of the mass required to cause a thermonuclear runaway (TNR). Overall our results support a model in which a large accretion disc acts as a reservoir with increased accretion rate onto the central white dwarf during disc high states, ultimately leading to a TNR explosion, which now seems to be imminent.
We present an observational approach for the independent detection of the prompt optical emission of long gamma-ray bursts (GRBs). For this purpose, we explore the potential of the Large Array Survey Telescope (LAST). This array of small optical telescopes can be used to scan a wide region of the sky, and to focus on a smaller field of view with increased sensitivity, as needed. The modularity of the array facilitates dynamic scanning of multiple fields, by shifting telescope pointing directions with high cadence. This can significantly increase the effective sky-coverage of a blind survey on short time scales. For events associated with gamma-ray counterparts, the valuable early-time data can supplement high-energy observations. Regardless of gamma-ray association, detections can potentially be used to explore various phenomena associated with GRBs, such as orphan afterglows; dirty fireballs; and choked jets. We simulate a sample of GRBs and their respective optical signals at early times. After accounting for dynamic cadence, the light curves are given as input to a machine learning classifier, used to identify astrophysical transients. We find that by dedicating half of a LAST array to a blind search, one would expect to discover 7-11 GRBs per year, corresponding to an approximate intrinsic event rate of 0.12 per square degree per year.
Observations, mainly of outbursts in dwarf novae, imply that the anomalous viscosity in highly ionized accretion discs is magnetic in origin, and requires that the plasma $\beta \sim 1$. Until now most simulations of the magnetic dynamo in accretion discs have used a local approximation (known as the shearing box). While these simulations demonstrate the possibility of a self-sustaining dynamo, the magnetic activity generated in these models saturates at $\beta \gg 1$. This long-standing discrepancy has previously been attributed to the local approximation itself. There have been recent attempts at simulating magnetic activity in global accretion discs with parameters relevant to the dwarf novae. These too find values of $\beta \gg 1$. We speculate that the tension between these models and the observations may be caused by numerical magnetic diffusivity. As a pedagogical example, we present exact time-dependent solutions for the evolution of weak magnetic fields in an incompressible fluid subject to linear shear and magnetic diffusivity. We find that the maximum factor by which the initial magnetic energy can be increased depends on the magnetic Reynolds number as ${\mathcal R}_{\rm m}^{2/3}$. We estimate that current global numerical simulations of dwarf nova discs have numerical magnetic Reynolds numbers around 6 orders of magnitude less than the physical value found in dwarf nova discs of ${\mathcal R}_{\rm m} \sim 10^{10}$. We suggest that, given the current limitations on computing power, expecting to be able to compute realistic dynamo action in observable accretion discs using numerical MHD is, for the time being, a step too far.
We report the discovery of X-ray polarization from the X-ray-bright thread/filament G0.13-0.11 in the Galactic Center region. This filament features a bright hard X-ray source, most plausibly a Pulsar Wind Nebula (PWN), and an extended and structured diffuse component. Combining the polarization signal from IXPE with the imaging/spectroscopic data from Chandra, we find that X-ray emission of G0.13-0.11 is highly polarized PD=$57(\pm18)$\% in the 3-6 keV band, while the polarization angle is PA=$21^\circ(\pm9^\circ)$. This high degree of polarization proves the synchrotron origin of the X-ray emission from G0.13-0.11. In turn, the measured polarization angle implies that the X-ray emission is polarized approximately perpendicular to a sequence of non-thermal radio filaments that may be part of the Galactic Center Radio Arc. The magnetic field of the order of $100\,{\rm\mu G}$ appears to be preferentially ordered along the filaments. The above field strength is the fiducial value that makes our model self-consistent, while the other conclusions are largely model-independent.
The nearby type II supernova, SN2023ixf in M101 exhibits signatures of early-time interaction with circumstellar material in the first week post-explosion. This material may be the consequence of prior mass loss suffered by the progenitor which possibly manifested in the form of a detectable pre-supernova outburst. We present an analysis of the long-baseline pre-explosion photometric data in $g$, $w$, $r$, $i$, $z$ and $y$ filters from Pan-STARRS as part of the Young Supernova Experiment, spanning $\sim$5,000 days. We find no significant detections in the Pan-STARRS pre-explosion light curve. We train a multilayer perceptron neural network to classify pre-supernova outbursts. We find no evidence of eruptive pre-supernova activity to a limiting absolute magnitude of $-7$. The limiting magnitudes from the full set of $gwrizy$ (average absolute magnitude $\approx$-8) data are consistent with previous pre-explosion studies. We use deep photometry from the literature to constrain the progenitor of SN2023ixf, finding that these data are consistent with a dusty red supergiant (RSG) progenitor with luminosity $\log\left(L/L_\odot\right)$$\approx$5.12 and temperature $\approx$3950K, corresponding to a mass of 14-20 M$_\odot$
In turbulent magnetized plasmas, charged particles can be accelerated to high energies through their interactions with the turbulent motions. As they do so, they draw energy from the turbulence, possibly up to the point where they start modifying the turbulent cascade. Stochastic acceleration then enters a nonlinear regime because turbulence damping back-reacts in turn on the acceleration process. This article develops a phenomenological model to explore this phenomenon and its consequences on the particle and turbulent energy spectra. We determine a criterion that specifies the threshold of nonthermal particle energy density and the characteristic momentum beyond which back-reaction becomes effective. Once the back-reaction sets in, the turbulence cascade becomes damped below a length scale that keeps increasing in time. The accelerated particle momentum distribution develops a near power-law of the form ${\rm d}n/{\rm d}p\propto p^{-s}$ with $s\sim2$ beyond the momentum at which back-reaction first sets in. At very high energies, where the gyroradius of accelerated particles becomes comparable to the outer scale of the turbulence, the energy spectrum can display an even harder spectrum with $s\sim 1.3-1.5$ over a short segment. The low-energy part of the spectrum, below the critical momentum, is expected to be hard ($s\sim 1$ or harder), and shaped by any residual acceleration process in the damped region of the turbulence cascade. This characteristic broken power-law shape with $s\sim 2$ at high energies may find phenomenological applications in various high-energy astrophysical contexts.
The origin of the diffuse flux of TeV-PeV astrophysical neutrinos is still unknown. The $\gamma$-ray blazar PKS 0735+178, located outside the 90\% localization region at 2.2 deg from the best-fit IC-211208A event, was found to be flaring across all wavebands. In addition to leptonic synchrotron (SYN) and synchrotron self-Compton (SSC) emission, we invoke photohadronic ($p\gamma$) interactions inside the jet to model the spectral energy distribution (SED) and neutrino emission. We analyze the 100 days $\gamma$-ray and X-ray data and 10 days around the neutrino event is chosen to generate the broadband SED. The temporal light curve indicates that the source was in a high state in optical, UV, $\gamma$-ray, and X-ray frequencies during the neutrino detection epoch. In the one-zone lepto-hadronic model, the SSC photons do not provide enough seed photons for $p\gamma$ interactions to explain the neutrino event. However, including an external photon field yields a neutrino event rate of 0.12 in 100 days, for the IceCube detector, using physically motivated values of the magnetic field, an external photon field peaking at optical wavelength, and other jet parameters. The radiation from secondary electrons at X-ray energies severely constrains the neutrino flux to a lower value than found in previous studies. Moreover, the flux of high-energy $\gamma$-rays at GeV energies from the decay of neutral pions is subdominant at the high-energy peak of the SED, suggesting a higher correlation of neutrinos flux with X-ray flux is plausible.
We study the effect of the isovector-scalar meson $a_0$(980) on the properties of nuclear matter and the neutron star (NS) matter by constructing a parity doublet model with including the $a_0$ meson based on the chiral SU(2)$_L\times$SU(2)$_R$ symmetry. We also include the $\omega$-$\rho$ mixing contribution to adjust the slope parameter at the saturation. We find that, when the chiral invariant mass of nucleon $m_0$ is smaller than about 800 MeV, the existence of $a_0$(980) enlarges the symmetry energy by strengthening the repulsive $\rho$ meson coupling. On the other hand, for large $m_0$ where the Yukawa coupling of $a_0$(980) to nucleon is small, the symmetry energy is reduced by the effect of $\omega$-$\rho$ mixing. We then construct the equation of state (EoS) of a neutron star matter to obtain the mass-radius relation of NS. We find that, in most choices of $m_0$, the existence of $a_0$(980) stiffens the EoS and makes the radius of NS larger. We then constrain the chiral invariant mass of nucleon from the observational data of NS, and find that $580 \,\text{ MeV} \lesssim m_0 \lesssim 860 \,\text{ MeV} $ for $L_0=57.7$ MeV.
We present a Bayesian parameter estimation progress to infer the stellar mass binary black hole properties by TianQin, LISA, and TianQin+LISA.Two typical stellar mass black hole binary systems, GW150914 and GW190521 are chosen as the fiducial sources. In this work, we establish the ability of TianQin to infer the parameters of those systems and first apply the full frequency response in TianQin's data analysis. We obtain the parameter estimation results and explain the correlation between them. We also find the TianQin+LISA could marginally increase the parameter estimation precision and narrow the $1\sigma$ area compared with TianQin and LISA individual observations. We finally demonstrate the importance of considering the effect of spin when the binaries have a nonzero component spin and great deviation will appear especially on mass, coalescence time and sky location.
The tera-electronvolt (TeV) light curve of gamma-ray burst (GRB) 221009A shows an unprecedentedly rapid rise at the beginning epoch. This phenomenon could be due to the strong absorption of photons and electrons within the emitting region. As the external shock expands outwards and the radius increases, the volume of matter also increases, leading to a gradual decrease in the optical depth for TeV photons. We explore several possibilities for the physical origin of this peculiar behavior. We calculate the optical depth for TeV photons due to annihilation with lower energy photons in the external shock and scattering by electrons produced via cascading of the TeV emission. Even under aggressive assumptions, we find the optical depths for these processes are orders of magnitude too small to explain the observed light curve. Other sources of absorbers, such as electrons in the ejecta or external shock, also do not yield sufficient optical depths. Therefore, the origin of the early peculiar TeV light curve remains uncertain.
The black hole transient GRS 1915+105 entered a new phase of activity in 2018, generally characterised by low X-ray and radio fluxes. This phase has been only interrupted by episodes of strong and variable radio emission, during which high levels of X-ray absorption local to the source were measured. We present 18 epochs of near-infrared spectroscopy (2018-2023) obtained with GTC/EMIR and VLT/X-shooter, spanning both radio-loud and radio-quiet periods. We demonstrate that radio-loud phases are characterised by strong P-Cygni line profiles, indicative of accretion disc winds with velocities of up to $\mathrm{\sim 3000~km~s^{-1}}$. This velocity is consistent with those measured in other black hole transients. It is also comparable to the velocity of the X-ray winds detected during the peak outburst phases in GRS 1915+105, reinforcing the idea that massive, multi-phase outflows are characteristic features of the largest and most powerful black hole accretion discs. Conversely, the evolution of the Br$\gamma$ line profile during the radio-quiet phases follows the expected trend for accretion disc lines in a system that is gradually decreasing its intrinsic luminosity, exhibiting weaker intensities and more pronounced double-peaks.
A superradiant cloud of ultralight bosons near a rotating black hole provides a smoking gun for particle physics in the infrared. However, tidal perturbations from a nearby binary companion can destabilise the boson cloud and even terminate superradiance. In this work, we consider the backreaction of superradiance termination to the dynamics of general binary orbits parametrised by their semi-latus rectum, eccentricity and inclination angle. Our analysis focuses on Extreme Mass Ratio Inspiral (EMRI) systems and employs the period-average approximation to derive evolution equations of these binary parameters in the Newtonian limit. We find that the binary evolution history can be significantly modulated by the backreaction towards large circular equatorial orbits with reduced termination rate. This process can generically happen even away from the resonance bands. Our work therefore serves as a first step towards probing ultralight bosons through the statistics of EMRI binary parameters in the future.
The origin of repeating fast radio bursts (RFRBs) is still a mystery. We propose that short-lived RFRBs might be triggered from the tidal disruption of white dwarfs (WDs) by intermediate-mass black holes (BHs). In this model, we show that the remnant WD clusters after tidal collapse cuts the magnetic lines on the BH accretion discs, and during each fall of the clump, so that electrons are torn from the surface of the mass and instantly accelerated to the relativistic energy. The subsequent movement of these electrons along magnetic field lines will result in coherent curvature radiation. This short-lived radio transients might accompany with the accretion process. The luminosity and the timescale can be estimated to be $L_\mathrm{tot}\sim 1.96\times10^{40}~{\rm erg~s^{-1}}$ and $\Delta t\sim1.14~{\rm ms}$, respectively, which are consistent with the typical properties of RFRBs. Moreover, the total event rate of our model for generating RFRBs might be as high as $\sim 10~\rm {yr^{-1}~Gpc^{-3}}$.
Utilizing Planck polarized dust emission maps at 353 GHz and new large-area maps of the neutral hydrogen (HI) cold neutral medium (CNM) fraction ($f_\mathrm{CNM}$), we investigate the relationship between dust polarization fraction ($p_{353}$) and $f_\mathrm{CNM}$ in the diffuse high latitude ($|b|>30^{\circ}$) sky. We find that the correlation between $p_{353}$ and $f_\mathrm{CNM}$ is qualitatively distinct from the $p_{353}$-HI column density ($N_\mathrm{H\,I}$) relationship. At low column densities ($N_\mathrm{H\,I}<4\times10^{20}~\mathrm{cm^{-2}}$) where $p_{353}$ and $N_\mathrm{H\,I}$ are uncorrelated, there is a strong positive $p_{353}$-$f_\mathrm{CNM}$ correlation. We fit the $p_{353}$-$f_{\rm CNM}$ correlation with data-driven models to constrain the degree of magnetic field disorder between phases along the line-of-sight. We argue that an increased magnetic field disorder in the warm neutral medium (WNM) relative to the CNM best explains the positive $p_{353}$-$f_\mathrm{CNM}$ correlation in diffuse regions. Modeling the CNM-associated dust column as being maximally polarized, with a polarization fraction $p_{\rm CNM} \sim$ 0.2, we find that the best-fit mean polarization fraction in the WNM-associated dust column is 0.22$p_{\rm CNM}$. The model further suggests that a significant $f_{\rm CNM}$-correlated fraction of the non-CNM column (an additional ~18.4\% of the HI mass on average) is also more magnetically ordered, and we speculate that the additional column is associated with the unstable medium (UNM). Our results constitute the first large-area constraint on the average relative disorder of magnetic fields between the neutral phases of the ISM, and are consistent with the physical picture of a more magnetically aligned CNM column forming out of a disordered WNM.
The oldest stars in the Milky Way (born in the first few billion years) are expected to have a high density in the inner few kpc, spatially overlapping with the Galactic bulge. We use spectroscopic data from the Pristine Inner Galaxy Survey (PIGS) to study the dynamical properties of ancient, metal-poor inner Galaxy stars. We compute distances using StarHorse, and orbital properties in a barred Galactic potential. With this paper, we release the spectroscopic AAT/PIGS catalogue (13 235 stars). We find that most PIGS stars have orbits typical for a pressure-supported population. The fraction of stars confined to the inner Galaxy decreases with decreasing metallicity, but many very metal-poor stars (VMP, [Fe/H] < -2.0) stay confined (~ 60% stay within 5 kpc). The azimuthal velocity v$_\phi$ also decreases between [Fe/H] = -1.0 and -2.0, but is constant for VMP stars (at ~ 40 km/s). The carbon-enhanced metal-poor (CEMP) stars in PIGS appear to have similar orbital properties compared to normal VMP stars. Our results suggest a possible transition between two spheroidal components - a more metal-rich, more concentrated, faster rotating component, and a more metal-poor, more extended and slower/non-rotating component. We propose that the former may be connected to pre-disc in-situ stars (or those born in large building blocks), whereas the latter may be dominated by contributions from smaller galaxies. This is an exciting era where large metal-poor samples, such as in this work (as well as upcoming surveys, e.g., 4MOST), shed light on the earliest evolution of our Galaxy.
We use numerical simulations to model Gaia DR3 data with the aim of constraining the Milky Way bar and spiral structure parameters. We show that both the morphology and the velocity field in Milky Way-like galactic disc models are strong functions of time, changing dramatically over a few tens of Myr. This suggests that by finding a good match to the observed radial velocity field, v_R(x,y), we can constrain the bar-spiral orientation. Incorporating uncertainties into our models is necessary to match the data; most importantly, a heliocentric distance uncertainty above 10-15% distorts the bar's shape and $v_R$ quadrupole pattern morphology, and decreases its apparent angle with respect to the Sun-Galactocentric line. An excellent match to the \Gaia DR3 $v_R(x,y)$ field is found for a simulation with a bar length R_b~3.6 kpc. We argue that the data are consistent with a MW bar as short as ~3 kpc, for moderate strength inner disc spiral structure (A_2/A_0~0.25) or, alternatively, with a bar length up to ~5.2 kpc, provided that spiral arms are quite weak (A_2/A_0~0.1), and is most likely in the process of disconnecting from a spiral arm. We demonstrate that the bar angle and distance uncertainty can similarly affect the match between our models and the data - a smaller bar angle (20 deg instead of 30 deg) requires smaller distance uncertainty (20% instead of 30%) to explain the observations. Fourier components of the face-on density distribution of our models suggest that the MW does not have strong m=1 and/or m=3 spirals inside the solar radius.
``Extremely red quasars'' (ERQs) are a non-radio-selected, intrinsically luminous population of quasars at cosmic noon selected by their extremely red colour from rest-frame UV to mid-IR. ERQs are uniquely associated with exceptionally broad and blueshifted [\ion{O}{III}]\,$\lambda$5007 emission reaching speeds $>$6000\,km\,s$^{-1}$. We obtained laser-guided adaptive optics integral-field spectroscopic observations using Keck/OSIRIS and Gemini/NIFS of a sample of 10 ERQs with bolometric luminosities (10$^{47.0}$\textendash10$^{47.9}$)\,erg\,s$^{-1}$ at $z\sim$~(2.3\textendash3.0). The goal is to measure the sizes and spatially-resolved kinematics of the [\ion{O}{III}]-emitting regions. We study the surface brightness maps and aperture-extracted spectra and model the point-spread functions. We identify signs of merger activities in the continuum emissions. We identify physically distinct [\ion{O}{III}] kinematic components that are bimodal and respectively trace ERQ-driven outflows of velocity dispersion $\gtrsim$250\,km\,s$^{-1}$ and dynamically quiescent interstellar media. We find that the ERQ-driven ionized outflows are typically at $\sim$1\,kpc scales whereas the quiescent ionized gas extend to a few kpc. Compared to other luminous quasars the extremely fast ERQ-driven [\ion{O}{III}] outflows tend to be more compact, supporting the notion that ERQs are in a young stage of quasar/galaxy evolution and represent systems with unique physical conditions beyond orientation differences with other quasar populations. The kinematically quiescent [\ion{O}{III}] emissions in ERQs tend to be spatially-resolved but less extended than in other luminous quasars, which can be explained by global and patchy dust obscuration. The hint of ionization cones suggests some of the obscuration can be partially explained by a patchy torus.
Massive infrared dark clouds (IRDCs) are considered to host the earliest stages of high-mass star formation. In particular, 70 $\mu$m dark IRDCs are the colder and more quiescent clouds. At a scale of about 5000 au using formaldehyde (H2CO) emission, we investigate the kinetic temperature of dense cores in 12 IRDCs obtained from the pilot ALMA Survey of 70 $\mu$m dark High-mass clumps in Early Stages (ASHES). Compared to 1.3 mm dust continuum and other molecular lines, such as C18O and deuterated species, we find that H2CO is mainly sensitive to low-velocity outflow components rather than to quiescent gas expected in the early phases of star formation. The kinetic temperatures of these components range from 26 to 300 K. The Mach number reaches about 15 with an average value of about 4, suggesting that the velocity distribution of gas traced by H2CO is significantly influenced by a supersonic non-thermal component. In addition, we detect warm line emission from HC3N and OCS in 14 protostellar cores, which requires high excitation temperatures (Eu/k ~ 100 K). These results show that some of the embedded cores in the ASHES fields are in an advanced evolutionary stage, previously unexpected for 70 $\mu$m dark IRDCs.
The Breakthrough Listen search for intelligent life is, to date, the most extensive technosignature search of nearby celestial objects. We present a radio technosignature search of the centers of 97 nearby galaxies, observed by Breakthrough Listen at the Robert C. Byrd Green Bank Telescope. We performed a narrowband Doppler drift search using the turboSETI pipeline with a minimum signal-to-noise parameter threshold of 10, across a drift rate range of $\pm$ 4 Hz\ $s^{-1}$, with a spectral resolution of 3 Hz and a time resolution of $\sim$ 18.25 s. We removed radio frequency interference by using an on-source/off-source cadence pattern of six observations and discarding signals with Doppler drift rates of 0. We assess factors affecting the sensitivity of the Breakthrough Listen data reduction and search pipeline using signal injection and recovery techniques and apply new methods for the investigation of the RFI environment. We present results in four frequency bands covering 1 -- 11 GHz, and place constraints on the presence of transmitters with equivalent isotropic radiated power on the order of $10^{26}$ W, corresponding to the theoretical power consumption of Kardashev Type II civilizations.
We present a $^{12}$CO($J$=2-1) survey of 60 local galaxies using data from the Atacama Large Millimeter/submillimeter Compact Array as part of the Extragalactic Database for Galaxy Evolution: the ACA EDGE survey. These galaxies all have integral field spectroscopy from the CALIFA survey. Compared to other local galaxy surveys, ACA EDGE is designed to mitigate selection effects based on CO brightness and morphological type. Of the 60 galaxies in ACA EDGE, 36 are on the star-formation main sequence, 13 are on the red sequence, and 11 lie in the ``green valley" transition between these sequences. We test how star formation quenching processes affect the star formation rate (SFR) per unit molecular gas mass, SFE$_{\rm mol}=$SFR/$M_{\rm mol}$, and related quantities in galaxies with stellar masses $10\leq$log[$M_\star/$M$_\odot$]$\leq11.5$ covering the full range of morphological types. We observe a systematic decrease of the molecular-to-stellar mass fraction ($R^{\rm mol}_{\star}$) with decreasing level of star formation activity, with green valley galaxies having also lower SFE$_{\rm mol}$ than galaxies on the main sequence. On average, we find that the spatially resolved SFE$_{\rm mol}$ within the bulge region of green valley galaxies is lower than in the bulges of main sequence galaxies if we adopt a constant CO-to-H$_2$ conversion factor, $\alpha_{\rm CO}$. While efficiencies in main sequence galaxies remain almost constant with galactocentric radius, in green valley galaxies we note a systematic increase of SFE$_{\rm mol}$, $R^{\rm mol}_{\star}$, and specific star formation rate, sSFR, with increasing radius. Our results suggest that although gas depletion (or removal) seems to be the most important driver of the star-formation quenching in galaxies transiting through the green valley, a reduction in star formation efficiency is also required during this stage.
It has been suggested that the bulge-to-total stellar mass ratio or feedback from black holes (BHs), traced by the BH-to-(total stellar) mass ratio, might establish a galaxy's specific star formation rate (sSFR). We reveal that a galaxy's morphology -- reflecting its formation history, particularly accretions and mergers -- is a far better determinant of the sSFR. Consequently, we suggest that galaxy formation models which regulate the sSFR primarily through BH feedback prescriptions or bulge-regulated disc fragmentation consider acquisitions and mergers which establish the galaxy morphology. We additionally make several new observations regarding current ($z\sim0$) star-formation rates. (i) Galaxies with little to no star formation have bulges with an extensive range of stellar masses; bulge mass does not dictate presence/absence on the `star-forming main sequence'. (ii) The (wet merger)-built, dust-rich S0 galaxies are the `green valley' bridging population between elliptical galaxies on the `red sequence' and spiral galaxies on the blue star-forming main sequence. (iii) The dust-poor S0 galaxies are not on the star-forming main sequence nor in the `green valley'. Instead, they wait in the field for gas accretion and/or minor mergers to transform them into spiral galaxies. Mid-infrared sample selection can miss these (primordial) low dust-content and low stellar-luminosity S0 galaxies. Finally, the appearance of the quasi-triangular-shaped galaxy-assembly sequence, previously dubbed the Triangal, which tracks the morphological evolution of galaxies, is revealed in the sSFR-(stellar mass) diagram.
The observational data of high redshift galaxies become increasingly abundant, especially since the operation of the James Webb Space Telescope (JWST), which allows us to verify and optimize the galaxy formation model at high redshifts. In this work, we investigate the merging history of massive galaxies at $3 < z < 6$ using a well-developed semi-analytic galaxy formation catalogue. We find that the major merger rate increases with redshift up to 3 and then flattens. The fraction of wet mergers, during which the sum of the cold gas mass is higher than the sum of the stellar mass in two merging galaxies, also increases from $\sim$ 34\% at $z = 0$ to 96\% at $z = 3$. Interestingly, almost all major mergers are wet at $z > 3$ . This can be attributed to the high fraction ($> 50\%$) of cold gas at $z > 3$. In addition, we study some special systems of massive merging galaxies at $3 < z < 6$, including the massive gas-rich major merging systems and extreme dense proto-clusters, and investigate the supermassive black hole-dark matter halo mass relation and dual AGNs. We find that the galaxy formation model reproduces the incidence of those observed massive galaxies, but fails to reproduce the relation between the supermassive black hole mass and the dark matter halo mass at $z \sim 6$. The latter requires more careful estimates of the supermassive black hole masses observationally. Otherwise, it could suggest modifications of the modeling of the supermassive black hole growth at high redshifts.
We present a systematic study of the putative hot gas corona around late-type galaxies (LTGs) residing in the Virgo cluster, based on archival Chandra observations. Our sample consists of 21 nearly edge-on galaxies representing a star formation rate (SFR) range of ($0.2-3\rm~M_\odot~yr^{-1}$) a stellar mass ($M_*$) range of $(0.2-10) \times 10^{10}\rm~M_{\odot}$, the majority of which have not been explored with high-sensitivity X-ray observations so far. Significant extraplanar diffuse X-ray (0.5-2 keV) emission is detected in only three LTGs, which are also the three galaxies with the highest SFR. A stacking analysis is performed for the remaining galaxies without individual detection, dividing the whole sample into two subsets based on SFR, stellar mass, or specific SFR. Only the high-SFR bin yields a significant detection, which has a value of $L\rm_X \sim3\times10^{38}\rm~erg~s^{-1}$ per galaxy. The stacked extraplanar X-ray signals of the Virgo LTGs are consistent with the empirical $L\rm_X - SFR$ and $L\rm_X - M_*$ relations found among highly inclined disk galaxies in the field, but appear to be systematically lower than that of a comparison sample of simulated cluster star-formation galaxies identified from the Illustris-TNG100 simulation. The apparent paucity of hot gas coronae in the sampled Virgo LTGs might be understood as the net outcome of the long-lasting effect of ram pressure stripping exerted by the hot intra-cluster medium and in-disk star-forming activity acting on shorter timescales. A better understanding of the roles of environmental effects in regulating the hot gas content of cluster galaxies invites sensitive X-ray observations for a large galaxy sample.
We present a study of blue straggler stars (BSSs) of open cluster NGC 7142 using AstroSat/UVIT data and other archival data. Using a machine learning-based algorithm, ML-MOC, on Gaia DR3 data, we find 546 sources as cluster members. Based on the location on the Gaia color-magnitude diagram, we identify ten BSS candidates, also detected in UVIT/F148W filter. We study the variable nature of BSSs by constructing their light curves using the TESS data. Two BSSs reported as eclipsing binaries in Gaia DR3 are confirmed to be eclipsing binaries based on our analysis and also show the presence of hot companions as per the multi-wavelength spectral energy distributions (SEDs). The physical parameters of the hot companions of these two BSSs derived by fitting binary models to their light curves and those derived from the SEDs are found to be in good agreement. Additionally, five more BSSs in the cluster shows UV excess, four of which are likely to have a hot companion based on SEDs. The hot companions with the estimated temperatures $\sim$14000 $-$ 28000 K, radii $\sim$0.01 $-$ 0.05 R$_{\odot}$, and luminosities $\sim$0.03 $-$ 0.1 L$_{\odot}$, are inferred to be extremely low mass ($<$ 0.2 M$_{\odot}$), low-mass (0.2 $-$ 0.4 M$_{\odot}$), normal-mass (0.4 $-$ 0.6 M$_{\odot}$), and high-mass ($>$ 0.6 M$_{\odot}$) white dwarfs (WD). For the first time in an open cluster, we find the entire range of masses in WDs found as hot companions of BSSs. These masses imply that the Case-A/Case-B mass transfer as well as merger are responsible for the formation of at least 60$\%$ of the BSSs of this cluster.
We report a faint non-axisymmetric structure in NGC\,1087 through the use of JWST Near Infrared Camera { (NIRCam)}, with an associated kinematic counterpart observed as an oval distortion in the stellar velocity map, \ha~and CO~$J=2\rightarrow1$ velocity fields. This structure is not evident in the MUSE optical continuum images but only revealed in the near-IR with the F200W and F300M band filters at $2\mu$m and $3\mu$m respectively. Due to its elongation, this structure resembles a stellar bar although with remarkable differences with respect to conventional stellar bars. Most of the near-IR emission is concentrated within $6\arcsec~\sim500$~pc with a maximum extension up to 1.2~kpc. The spatial extension of the large-scale non-circular motions is coincident with the bar, which undoubtedly confirms the presence of a non-axisymmetric perturbation in the potential of NGC\,1087. The oval distortion is enhanced in CO due to its dynamically cold nature rather than in \ha. We found that the kinematics in all phases including stellar, ionized and molecular, can be described simultaneously by a model containing a bisymmetric perturbation; however, we find that an inflow model of gas along the bar major axis is also likely. Furthermore the molecular mass inflow rate associated can explain the observed star formation rate in the bar. This reinforces the idea that bars are mechanisms for transporting gas and triggering star formation. This work contributes to our understanding of non-axisymmetry in galaxies using the most sophisticated data so far.
The detections of Lyman-$\alpha$ ($\rm Ly\alpha$) emission in galaxies with redshifts above 5 are of utmost importance for constraining the cosmic reionization timeline, yet such detections are usually based on slit spectroscopy. Here we investigate the significant bias induced by slit placement on the estimate of $\rm Ly\alpha$ escape fraction ( $f_{\rm esc}^{\mathrm{Ly\alpha}}$), by presenting a galaxy (dubbed A2744-z6Lya) at $z=5.66$ where its deep JWST NIRSpec prism spectroscopy completely misses the strong $\rm Ly\alpha$ emission detected in the MUSE data. A2744-z6Lya exhibits a pronounced UV continuum with an extremely steep spectral slope of $\beta=-2.574_{-0.008}^{+0.008}$, and it has a stellar mass of $\mathrm{\sim10^{8.82}~M_\odot}$, a star-formation rate of $\mathrm{\sim8.35~M_\odot yr^{-1}}$ and gas-phase metallicity of $\mathrm{12+log\,(O/H)\sim7.88}$. The observed flux and rest-frame equivalent width of its Ly$\alpha$ from MUSE spectroscopy are $1.2\times \rm 10^{-16} erg~s^{-1}cm^{-2}$ and 75\r{A}, equivalent to $f_{\rm esc}^{\mathrm{Ly\alpha}}=78\pm4 \%$. However, its Ly$\alpha$ non-detection from JWST NIRSpec gives a 5-$\sigma$ upper limit of $<13 \%$, in stark contrast to that derived from MUSE. To explore the reasons for this bias, we perform spatially resolved stellar population analysis of A2744-z6Lya using the JWST NIRCam imaging data to construct 2-dimensional maps of SFR, dust extinction and neutral hydrogen column density. We find that the absence of Ly$\alpha$ in the slit regions probably stems from both the resonance scattering effect of neutral hydrogen and dust extinction. Through analyzing an extreme case in detail, this work highlights the important caveat of inferring $f_{\rm esc}^{\mathrm{Ly\alpha}}$ from slit spectroscopy, particularly when using the JWST multiplexed NIRSpec microshutter assembly.
We report on recent results from our successful and pioneering observational program with ALMA to study emerging ultracom pact HII regions of pre-Planetary Nebulae (pPNe) using mm-wavelength recombination lines (mRRLs) as new optimal tracers. We focus on our study of two poster-child pPNe, namely, M2-9 and CRL618. We reveal the structure and kinematics of the en igmatic inner nebular regions of these objects with an unprecedented angular resolution down to 20-30mas (~15-30AU). For both targets, the ionized central regions are elongated along the main symmetry axis of the large-scale nebulae, consiste nt with bipolar winds, and show notable axial velocity gradients with expansion velocities of up to ~100km/s. The H30a pr ofiles exhibit time variability, reflecting changes in the physical properties and kinematics on scales of a few years. O ur ongoing analysis employs 3D, non-LTE radiative transfer modeling, providing a detailed description of the innermost la yers of these well known pPNe with exceptional clarity.
We present a study on the star formation histories (SFHs) of galaxies covering the range $10^{4}$ < M$_{\star}$/M$_{\odot}$ < $10^{12}$, leveraging full spectral fitting algorithms. Our sample consists of 31 dwarf galaxies from the SAMI-Fornax Survey with stellar masses between $10^{7}$-$10^{9.5} M_{\odot}$, early-type galaxies from the ATLAS$^{3D}$ project with stellar masses between $10^{10}$-$10^{12} M_{\odot}$, and dwarf galaxies that are satellites of Andromeda and the Milky Way, with $10^{4}$ < M$_{\star}$/M$_{\odot}$ < $10^{8}$. We find that galaxies from $10^{7}$-$10^{8} M_{\odot}$ exhibit the smallest star formation rates (SFRs), while the SFR increase as we move down or up in mass. In this sense, we find that some $10^{5} M_{\odot}$ galaxies have cumulative SFHs that are comparable to those of $10^{12} M_{\odot}$ galaxies. Our study shows that the evolution of giant galaxies is primarily governed by their internal properties, with timescales that do not depend on their environmental location. In contrast, dwarf galaxies below $10^{8} M_{\odot}$ can be significantly affected in dense environments, such as the inner regions of a cluster, that severely quench the galaxies before the assembly of their 50% present-day mass. We find that, only dwarfs with stellar masses between $10^{7}$-$10^{9} M_{\odot}$ actively form stars nowadays, while less massive galaxies seem to remain unaffected by the environment due to the expulsion of most of their gas at an early stage in their evolution. Our study highlights and corroborates a critical threshold around $10^{8}-10^{9} M_{\odot}$ in galaxy evolution from previous studies, separating more massive galaxies minimally impacted by the environment from those less massive galaxies quenched by it.
We present the discovery of the most distant OH megamaser to be observed in the main lines, using data from the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE) survey. At a newly measured redshift of $z = 0.7092$, the system has strong emission in both the 1665MHz ($L \approx 2500$ L$_{\odot}$) and 1667 MHz ($L \approx 4.5\times10^4$ L$_{\odot}$) transitions, with both narrow and broad components. We interpret the broad line as a high-velocity-dispersion component of the 1667 MHz transition, with velocity $v \sim 330$km s$^{-1}$ with respect to the systemic velocity. The host galaxy has a stellar mass of $M_{\star} = 2.95 \times 10^{10}$ M$_{\odot}$ and a star-formation rate of SFR = 371 M$_{\odot}$yr$^{-1}$, placing it $\sim 1.5$dex above the main sequence for star-forming galaxies at this redshift, and can be classified as an ultra-luminous infrared galaxy. Alongside the optical imaging data, which exhibits evidence for a tidal tail, this suggests that the OH megamaser arises from a system that is currently undergoing a merger, which is stimulating star formation and providing the necessary conditions for pumping the OH molecule to saturation. The OHM is likely to be lensed, with a magnification factor of $\sim 2.5$, and perhaps more if the maser emitting region is compact and suitably offset relative to the centroid of its host galaxy's optical light. This discovery demonstrates that spectral line mapping with the new generation of radio interferometers may provide important information on the cosmic merger history of galaxies.
We present results from the Very Long Baseline Array (VLBA) multi-frequency (1.6, 4.4, 8.6, 22 GHz), high-sensitivity (~25 microJy beam^-1), sub-parsec scale (<1 pc) observations and Spectral Energy Distributions (SEDs) for a sample of 12 local active galactic nuclei (AGNs), a subset from our previous volume-complete sample with hard X-ray (14-195 keV) luminosities above 10^42 erg s^-1, out to a distance of 40 Mpc. All 12 of the sources presented here were detected in the C (4.4 GHz) and X (8.6 GHz) bands, 75% in the L band(1.6 GHz), and 50% in the K band (22 GHz). Most sources showed compact, resolved/slightly resolved, central sub-parsec scale radio morphology, except a few with extended outflow-like features. A couple of sources have an additional component that may indicate the presence of a dual-core, single or double-sided jet or a more intricate feature, such as radio emission resulting from interaction with nearby ISM. The spectral slopes are mostly GHz-peaked or curved, with a few showing steep, flat, or inverted spectra. We found that in the sub-parsec scale, the GHz-peaked spectra belong to the low-accreting, radio-loud AGNs with a tendency to produce strong outflows, possibly small-scale jet, and/or have a coronal origin. In contrast, flat/inverted spectra suggest compact radio emission from highly-accreting AGNs' central region, possibly associated with radio-quiet AGNs producing winds/shocks or nuclear star formation in the vicinity of black holes.
The redshift evolution of bars is an important signpost of the dynamic maturity of disk galaxies. To characterize the intrinsic evolution safe from band-shifting effects, it is necessary to gauge how bar properties vary locally as a function of wavelength. We investigate bar properties in 16 nearby galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G) at ultraviolet, optical and mid-infrared wavebands. Based on the ellipticity and position angle profiles from fitting elliptical isophotes to the two-dimensional light distribution, we find that both bar length and ellipticity - the latter often used as a proxy for bar strength - increase at bluer wavebands. Bars are 9% longer in the B-band than at 3.6 um. Their ellipticity increases typically by 8% in the B-band, with a significant fraction (>40%) displaying an increase up to 35%. We attribute the increase in bar length to the presence of star forming knots at the end of bars: these regions are brighter in bluer bands, stretching the bar signature further out. The increase in bar ellipticity could be driven by the apparent bulge size: the bulge is less prominent at bluer bands, allowing for thinner ellipses within the bar region. Alternatively, it could be due to younger stellar populations associated to the bar. The resulting effect is that bars appear longer and thinner at bluer wavebands. This indicates that band-shifting effects are significant and need to be corrected for high-redshift studies to reliably gauge any intrinsic evolution of the bar properties with redshift.
We consider the periapsis shifts of bound orbits of stars on static clouds around a black hole. The background spacetime is constructed from a Schwarzschild black hole surrounded by a static and spherically symmetric self-gravitating system of massive particles, which satisfies all the standard energy conditions and physically models the gravitational effect of dark matter distribution around a nonrotating black hole. Using nearly circular bound orbits of stars, we obtain a simple formula for the precession rate. This formula explicitly shows that the precession rate is determined by a positive contribution (i.e., a prograde shift) from the conventional general-relativistic effect and a negative contribution (i.e., a retrograde shift) from the local matter density. The four quantities for such an orbit (i.e., the orbital shift angle, the radial oscillation period, the redshift, and the star position mapped onto the celestial sphere) determine the local values of the background model functions. Furthermore, we not only evaluate the precession rate of nearly circular bound orbits in several specific models but also simulate several bound orbits with large eccentricity and their periapsis shifts. The present exact model demonstrates that the retrograde precession does not mean any exotic central objects such as naked singularities or wormholes but simply the existence of significant energy density of matters on the star orbit around the black hole.
Axion dark matter (DM) is studied on the formation of supermassive black holes (SMBHs) at high red shift $z$. It is shown that the attractive self interaction of this DM may solve the tension between the high angular momentum of SMBH and its early time formation. We consider the ultra-light axion DM around $O(10^{-21})$ eV as its origin, which may also cause nano-Hz stochastic gravitational wave background recently observed.
The dynamics of the satellite systems of Milky-Way-like galaxies offer a useful means by which to study the galaxy formation process in the cosmological context. It has been suggested that the currently observed anisotropic distribution of the satellites in such galaxy systems is inconsistent with the concordance $\Lambda CDM$ cosmology model on the galactic scale if the observed satellites are random samples of the dark matter (DM) sub-halos that are nearly isotropically distributed around the central galaxy. In this study, we present original high-resolution zoom-in studies of central galaxies and satellite systems based upon initial conditions for the DM distribution from the Aquarius simulations but with substantial high-resolution baryon physics added. We find that the galaxy most like the Milky Way in this study does indeed contain a disk of satellites (DOS). Although one galaxy DOS system does not answer the question of how common such disks are, it does allow the opportunity to explore the properties and dynamics of the DOS system. Our investigation centers on the spatial arrangement (distances, angles, etc.) of satellites in this Milky-Way-like galaxy system with a specific emphasis on identifying and analyzing the disk-like structure along with its dynamical and morphological properties. Among the conclusions from this study, we find that the satellites and DM sub-halos in the galaxy simulations are anisotropically distributed. The dynamical properties of the satellites, however, indicate that the direction of the angular momentum vector of the whole satellite system is different from the normal direction of the fitted DOS and from the normal direction of the velocity dispersion of the system. Hence, the fitted DOS appears to be comprised of infalling sub-halos and is not a rotationally supported system.
We perform a structural decomposition of galaxies identified in three cosmological hydrodynamical simulations by applying Gaussian Mixture Models (GMMs) to the kinematics of their stellar particles. We study the resulting disc, bulge, and intra-halo light (IHL) components of galaxies whose host dark matter haloes have virial masses in the range $M_{200}=10^{11}$-- $10^{15}\,{\rm M_\odot}$. Our decomposition technique isolates galactic discs whose mass fractions, $f_{\rm disc}$, correlate strongly with common alternative morphology indicators; for example, $f_{\rm disc}$ is approximately equal to $\kappa_{{\rm co}}$, the fraction of stellar kinetic energy in co-rotation. The primary aim of our study, however, is to characterise the IHL of galaxies in a consistent manner and over a broad mass range, and to analyse its properties from the scale of galactic stellar haloes up to the intra-cluster light. Our results imply that the IHL fraction, $f_{\rm IHL}$, has appreciable scatter and is strongly correlated with galaxy morphology: at fixed stellar mass, the IHL of disc galaxies is typically older and less massive than that of spheroids. Above $M_{200}\approx 10^{13}\,{\rm M_\odot}$, we find, on average, $f_{\rm IHL}\approx 0.45$, albeit with considerable scatter. The transition radius beyond which the IHL dominates the stellar mass of a galaxy is roughly $30\,{\rm kpc}$ for $M_{200}\lesssim 10^{12.8}\,{\rm M_\odot}$, but increases strongly towards higher masses. However, we find that no alternative IHL definitions -- whether based on the ex-situ stellar mass, or the stellar mass outside a spherical aperture -- reproduce our dynamically-defined IHL masses.
Announcing the final release, v8, of the Milliquas (Million Quasars) quasar catalogue which presents all published quasars to 30 June 2023, including quasars from the first releases of the Dark Energy Spectroscopic Instrument (DESI) and the SDSS-DR18 Black Hole Mapper. Its totals are 907,144 type-I QSOs/AGN and 66,026 high-confidence (~99% likelihood) radio/X-ray associated quasar candidates. Type-II and Bl Lac type objects are also included, bringing the total count to 1,021,800. Gaia-EDR3 astrometry is given for most objects. The catalogue is available on NASA HEASARC and CDS and on its home page.
The recent discovery of barred spiral galaxies in the early universe ($z>2$) poses questions of how these structures form and how they influence galaxy evolution in the early universe. In this study, we investigate the morphology and kinematics of the far infrared (FIR) continuum and [CII] emission in BRI1335-0417 at $z\approx 4.4$ from ALMA observations. The variations in position angle and ellipticity of the isophotes show the characteristic signature of a barred galaxy. The bar, $3.3^{+0.2}_{-0.2}$ kpc long in radius and bridging the previously identified two-armed spiral, is evident in both [CII] and FIR images, driving the galaxy's rapid evolution by channelling gas towards the nucleus. Fourier analysis of the [CII] velocity field reveals an unambiguous kinematic $m=2$ mode with a line-of-sight velocity amplitude of up to $\sim30-40$ km s$^{-1}$; a plausible explanation is the disk's vertical bending mode triggered by external perturbation, which presumably induced the high star formation rate and the bar/spiral structure. The bar identified in [CII] and FIR images of the gas-rich disk galaxy ($\gtrsim 70$\% of the total mass within radius $R\approx 2.2$ disk scale lengths) suggests a new perspective of early bar formation in high redshift gas-rich galaxies -- a gravitationally unstable gas-rich disk creating a star-forming gaseous bar, rather than a stellar bar emerging from a pre-existing stellar disk. This may explain the prevalent bar-like structures seen in FIR images of high-redshift submillimeter galaxies.
Boxy/peanut (b/p) bulges, the vertically extended inner parts of bars, are ubiquitous in barred galaxies in the local Universe, including our own Milky Way. At the same time, a majority of external galaxies and the Milky Way also possess a thick-disc. However, the dynamical effect of thick-discs in the b/p formation and evolution is not fully understood. Here, we investigate the effect of thick-discs in the formation and evolution of b/ps by using a suite of N-body models of (kinematically cold) thin and (kinematically hot) thick discs. Within the suite of models, we systematically vary the mass fraction of the thick disc, and the thin-to-thick disc scale length ratio. The b/ps form in almost all our models via a vertical buckling instability, even in the presence of a massive thick disc. The thin disc b/p is much stronger than the thick disc b/p. With increasing thick disc mass fraction, the final b/p structure gets progressively weaker in strength and larger in extent. Furthermore, the time-interval between the bar formation and the onset of buckling instability gets progressively shorter with increasing thick-disc mass fraction. The breaking and restoration of the vertical symmetry (during and after the b/p formation) show a spatial variation -- the inner bar region restores vertical symmetry rather quickly (after the buckling) while in the outer bar region, the vertical asymmetry persists long after the buckling happens. Our findings also predict that at higher redshifts, when discs are thought to be thicker, b/ps would have more 'boxy-shaped' appearance than more 'X-shaped' appearance. This remains to be tested from future observations at higher redshifts.
Despite the promise of Neural Posterior Estimation (NPE) methods in astronomy, the adaptation of NPE into the routine inference workflow has been slow. We identify three critical issues: the need for custom featurizer networks tailored to the observed data, the inference inexactness, and the under-specification of physical forward models. To address the first two issues, we introduce a new framework and open-source software nbi (Neural Bayesian Inference), which supports both amortized and sequential NPE. First, nbi provides built-in "featurizer" networks with demonstrated efficacy on sequential data, such as light curve and spectra, thus obviating the need for this customization on the user end. Second, we introduce a modified algorithm SNPE-IS, which facilities asymptotically exact inference by using the surrogate posterior under NPE only as a proposal distribution for importance sampling. These features allow nbi to be applied off-the-shelf to astronomical inference problems involving light curves and spectra. We discuss how nbi may serve as an effective alternative to existing methods such as Nested Sampling. Our package is at https://github.com/kmzzhang/nbi.
Model-based approaches to imaging, like specialized image enhancements in astronomy, favour physics-based models which facilitate explanations of relationships between observed inputs and computed outputs. While this paper features a tutorial example, inspired by exoplanet imaging, that reveals embedded 2D fast Fourier transforms in an image enhancement model, the work is actually about the tensor algebra and software, or tensor frameworks, available for model-based imaging. The paper proposes a Ricci-notation tensor (RT) framework, comprising an extended Ricci notation, which aligns well with the symbolic dual-index algebra of non-Euclidean geometry, and codesigned object-oriented software, called the RTToolbox for MATLAB. Extensions offer novel representations for entrywise, pagewise, and broadcasting operations popular in extended matrix-vector (EMV) frameworks for imaging. Complementing the EMV algebra computable with MATLAB, the RTToolbox demonstrates programmatic and computational efficiency thanks to careful design of tensor and dual-index classes. Compared to a numeric tensor predecessor, the RT framework enables superior ways to model imaging problems and, thereby, to develop solutions.
This book was created as part of the SIRIUS B VERGE program to orient students to astrophysics as a broad field. The 2023-2024 VERGE program and the printing of this book is funded by the Women and Girls in Astronomy Program via the International Astronomical Union's North American Regional Office of Astronomy for Development and the Heising-Simons Foundation; as a result, this document is written by women in astronomy for girls who are looking to pursue the field. However, given its universal nature, the material covered in this guide is useful for anyone interested in pursuing astrophysics professionally.
The experiments were performed at bremsstrahlung end-point energies of 10-23 MeV with the beam from the MT-25 microtron with the use of the {\gamma}-activation technique. The experimental values of relative yields were compared with theoretical results obtained on the basis of TALYS with the standard parameters and the combined model of photonucleon reactions. Including isospin splitting in the combined model of photonucleon reactions allows to describe experimental data on reactions with proton escape in energies range from 10 to 23 MeV. Therefore, taking into account isospin splitting is necessary for a correct description of the decay of the GDR.
Gravitational waves, detected a century after they were first theorized, are spacetime distortions caused by some of the most cataclysmic events in the universe, including black hole mergers and supernovae. The successful detection of these waves has been made possible by ingenious detectors designed by human experts. Beyond these successful designs, the vast space of experimental configurations remains largely unexplored, offering an exciting territory potentially rich in innovative and unconventional detection strategies. Here, we demonstrate the application of artificial intelligence (AI) to systematically explore this enormous space, revealing novel topologies for gravitational wave (GW) detectors that outperform current next-generation designs under realistic experimental constraints. Our results span a broad range of astrophysical targets, such as black hole and neutron star mergers, supernovae, and primordial GW sources. Moreover, we are able to conceptualize the initially unorthodox discovered designs, emphasizing the potential of using AI algorithms not only in discovering but also in understanding these novel topologies. We've assembled more than 50 superior solutions in a publicly available Gravitational Wave Detector Zoo which could lead to many new surprising techniques. At a bigger picture, our approach is not limited to gravitational wave detectors and can be extended to AI-driven design of experiments across diverse domains of fundamental physics.
Calibration of pixel values is a fundamental step for accurate measurements in astronomical imaging. In astronomical jargon this is known as estimating zero point magnitude. Here, we introduce a newly added script in GNU Astronomy Utilities (Gnuastro) version 0.20 for the zero point magnitude estimation, named: astscript-zeropoint. The script offers numerous features, such as the flexibility to use either image(s) or a catalog as the reference dataset. Additionally, steps are parallelized to enhance efficiency for big data. Thanks to Gnuastro's minimal dependencies, the script is both flexible and portable. The figures of this research note are reproducible with Maneage, on the Git commit c89275e.
In this paper, we propose a novel method for distinguishing extraterrestrial intelligence (ETI) signals from radio frequency interference (RFI) by leveraging polarization features. We exploit the sinusoidal variation of the linearly polarized components of Stokes parameters with the parallactic angle as a characteristic signature of ETI signals, while such linearly polarized components remain relatively stable for terrestrial RFI. Typically, a minimum of 4-8 hours of observation time is required to detect these sinusoidal variations. The polarization approach in the search for extraterrestrial intelligence (SETI) also enables us to study the radio stellar bursts emitted by M-type stars as ancillary science, which is relevant to assessing the habitability of exoplanets. Compared to the frequency drift method, the polarization method effectively reduces the required observation time for signal identification while improving the signal identification process.
In this work we characterise the performance of a new search technique designed to be sensitive to the remnants of binary neutron star systems. Sensitivity estimates of the new method on simulated data are competitive against those of other work. Previous searches for a gravitational-wave signal from a possible neutron star remnant of the binary neutron star merger event GW170817 have focused on short ($<500$~s) and long duration (2.5~hr -- 8~day) signals. To date, no such post-merger signal has been detected. We introduce a new piecewise model which has the flexibility to accurately follow gravitational-wave signals which are rapidly evolving in frequency, such as those which may be emitted from young neutron stars born from binary neutron star mergers or supernovae. We investigate the sensitivity and computational cost of this piecewise model when used in a fully coherent 1800-second $\mathcal{F}$-statistic search on simulated data containing possible signals from the GW170817 remnant. The sensitivity of the search using the piecewise model is determined using simulated data, with noise consistent with the LIGO second observing run. Across a 100--2000~Hz frequency band, the model achieves a peak sensitivity of $h_{\text{rss}}^{50\%} = 4.4 \times 10^{-23} \text{Hz}^{-1/2}$ at 200~Hz, competitive with other methods. The computational cost of conducting the search, over a bank of $1.1 \times 10^{12}$ templates, is estimated at 10 days running on 100 CPU's.
This thesis aims at improving our understanding of the strong-field regime of gravity, where deviations from General Relativity (GR) are expected to be found on theoretical grounds. In particular, we have been concerned with the formulation and application of junction conditions (which govern stellar collapse, black-hole formation and the dynamics of more exotic compact objects, such as thin-shell wormholes), as well as with other viability criteria necessary for modified gravity theories and their solutions to be physically admissible (for instance, compatibility with gravitational-wave observations, stability or the avoidance singularities). First, we have studied stellar collapse in $f(R)$ gravity. By means of a systematic treatment of the relevant junction conditions, we have proven a series of stringent no-go results on the exterior space-time, which entail that some paradigmatic classes of vacuum metrics cannot represent space-time outside a collapsing dust star in metric $f(R)$ gravity. This could lead to potentially observable deviations with respect to GR. We have also provided an exhaustive derivation of the junction conditions in bi-scalar Poincar\'e gauge gravity, finding that the matching interface is allowed to host surface axial spin monopoles, as well as matter thin shells and double layers. This singular structure is richer than its counterparts in GR or $f(R)$ gravity, leading to possible interesting applications. In addition, we have had to resolve some procedural and mathematical subtleties in the junction-condition formalism. Finally, we have examined a wide class of metric $f(R)$ models, the so-called '$R_0$-degenerate models,' solved by all metrics with constant scalar curvature $R=R_0$. We have shown that they feature all sorts of shortcomings (such as previously-unforeseen strong-coupling instabilities) rendering their viability extremely limited.
We have obtained a new exact regular black hole solution for the EGB gravity coupled with nonlinear electrodynamics in AdS space. The numerical analysis of horizon structure suggests two horizons exist: Cauchy and event. We also study the thermal properties of this black hole, which satisfy the modified first law of thermodynamics. Moreover, we analyse the local and global stability of the black hole. The $P-V$ criticality and phase transition are also discussed. The critical exponents for the present model exactly match the mean field theory.
We develop a symmetric traversable wormhole model, integrating Einstein's gravitational coupling phantom field and a nonlinear electromagnetic field. This work indicates the emergence of negative ADM mass within a specific parameter range, coinciding with distinct alterations in the wormhole's spacetime properties. Despite violating the Null Energy Condition (NEC) and other energy conditions, the solution exhibits unique characteristics in certain energy-momentum tensor components, potentially accounting for the manifestation of negative mass.
The topic of quantum reference frames (QRFs) has attracted a great deal of attention in the recent literature. Potentially, the correct description of such frames is important for both the technological applications of quantum mechanics and for its foundations, including the search for a future theory of quantum gravity. In this letter, we point out potential inconsistencies in the mainstream approach to this subject and propose an alternative definition that avoids these problems. Crucially, we reject the notion that transformations between QRFs can be represented by unitary operators and explain the clear physical reasons for this. An experimental protocol, capable of empirically distinguishing between competing definitions of the term, is also proposed. The implications of the new model, for uncertainty relations, spacetime symmetries, gauge symmetries, the quantisation of gravity, and other foundational issues are discussed, and possible directions for future work in this field are considered.
We present a new formalism to solve the kinematical constraints due to Weyl invariance for CFTs in curved backgrounds and/or non-trivial states, and we apply it to thermal CFTs and to CFTs on squashed spheres. The ambient space formalism is based on constructing a class of geometric objects that are Weyl covariant and identifying them as natural building blocks of correlation functions. We construct (scalar) $n$-point functions and we illustrate the formalism with a detailed computation of 2-point functions. We compare our results for thermal 2-point functions with results that follow from thermal OPEs and holographic computations, finding exact agreement. In our holographic computation we also obtain the OPE coefficient of the leading double-twist contribution, and we discuss how the double-twist coefficients may be computed from the multi-energy-momentum contributions, given knowledge of the analytic structure of the correlator. The 2-point function for the CFT on squashed spheres is a new result. We also discuss the relation of our work to flat holography.
We analyse the renormalisation group flow of quantum gravity at sixth order in the derivative expansion within the background field approximation. Non-linear field redefinitions are used to ensure that only essential couplings flow. Working within the universality class of General Relativity, with a vanishing cosmological constant, redundant couplings are fixed to their values at the Gaussian fixed point. This reduces the theory space to two dynamical essential couplings given by Newton's and the Goroff-Sagnotti coupling. Furthermore, it implements the condition that no extra degrees of freedom are present beyond those of General Relativity, in contrast to higher derivative theories and derivative expansions in a conventional renormalisation scheme. We find a unique ultraviolet fixed point with a single relevant direction and analyse the phase diagram of the theory. Our results suggest resilience of the gravitational Reuter fixed point under the inclusion of higher order curvature invariants and show several signs of near-perturbativity. The regulator dependence of our results is investigated in detail and shows that qualitative and quantitative features are robust to a large extent.
We investigate what kind of Markovian quantum master equation (QME) in the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) form is realized under Poincar\'{e} symmetry. The solution of the Markovian QME is given by a quantum dynamical semigroup, for which we introduce invariance under Poincar\'{e} transformations. Using the invariance of the dynamical semigroup and applying the unitary representation of Poincar\'{e} group, we derive the Markovian QME for a relativistic massive spin-0 particle. Introducing the field operator of the massive particle and examining its evolution, we find that the field follows a dissipative Klein-Gordon equation. In addition, we show that any two local operators for spacelike separated regions commute with each other. This means that the microcausality condition is satisfied for the dissipative model of the massive particle.
Recent progress in holographic realization of strange metal transport has given us new insights into getting new black hole solutions. In this paper, we consider the $S$-completion and $ST$-completion of the Gubser-Rocha model. The dyonic black holes of the S-type Gubser-Rocha model come in families as $\mathbb{Z}_4$ quartets. For the $ST$-completion, solutions form pairs under $\mathbb{Z}_6$ symmetry. The charge vectors of the solutions in each family form a hexagon, realizing six-fold way in gravitational systems.
The strong cosmic censorship conjecture, which states that the evolution of generic initial data will always produce a globally hyperbolic spacetime, is hard to be tested by astronomical observations. In this paper, we study the appearance of the regular black hole without mass inflation, which violates the strong cosmic censorship conjecture. Since the Cauchy horizon is stable, the photons entering the two horizons of the regular black hole in the preceding companion universe can come out from the white hole in our universe. These rays create a novel multi-ring structure, which is significantly different from the image of the Schwarzschild black hole. This serves a potential method to test the strong cosmic censorship conjecture.
Detecting the environment around the supermassive black holes and tests of general relativity are important applications of extreme-mass-ratio inspirals (EMRIs). There is still a challenge to efficiently describe various "dirty" impacts on the inspirals like dark matter, gas, dipole radiation, electromagnetic interaction, and so on. In this Letter, we find the inherent linearity of the asymptotic solution of the inhomogeneous Teukolsky equation. Based on this property, we completely decouple the factors of the perturber and the background spacetime in the energy fluxes and waveforms. With the new decoupling form, the waveforms of EMRIs with non-geodesic motion in Kerr spacetime can be calculated conveniently. This will help to resolve the environment (including gas, field, dark matter, electromagnetic interaction, etc.) around the supermassive black holes and test general relativity.
In this article, we investigate the thermodynamic topology of some black holes, namely AdS Reissner Nordstrom (R-N), AdS Einstein-Gauss-Bonnet (EGB), and AdS Einstein-power-Yang-Mills (EPYM), from different frameworks: bulk-boundary (BB) and restricted phase space (RPS). Using the generalized off-shell Helmholtz free energy method, we calculate the thermodynamic topology of the selected black holes in each space separately and determine their topological classifications. We show that the addition of GB terms, dimensions, and other factors do not affect the topological classes of black holes in both spaces. The calculations and plots indicate that the AdS R-N and AdS EGB black holes show similar behavior and their topological numbers sets in both spaces, i.e., BB and RPS, are similar and equal to ($W=+1$). However, AdS EPYM black holes show an interesting behavior. In addition to BBT and RPS, we also consider the extended phase space thermodynamics (EPST) and evaluate the thermodynamic topology for AdS EPYM black hole. The changing ($r-\tau$) in both spaces shows similar behavior. Also, the topological number and the total topological numbers for this black hole in the BB, RPS and EPS thermodynamics are completely same, i,e., $(\omega_{BBT}=\omega_{RPS}=\omega_{EPST}=+1, -1)$ or $W_{BBT}=W_{RPS}=W_{EPST}=0$. An important point is that the Einstein-Yang-Mills black hole has thermodynamic topology equivalence in three spaces. The present result may be due to the non-linear YM charge parameter and the difference between the gauge and gravity corrections in the above black holes
We define gravitational multipoles for five-dimensional, stationary, and asymptotically flat vacuum metrics. We do this by generalizing Thorne's asymptotically Cartesian and mass-centered (ACMC) coordinate formalism to five dimensions, and prove that the multipoles defined in this way are unambiguously well-defined. We find that such five-dimensional metrics admit two towers of multipole tensors (as in four dimensions), which in the case of biaxial symmetry reduce to a tower of mass multipoles $M_\ell$, and two separate towers of current or angular momentum multipoles $S^{(1)}_\ell, S^{(2)}_\ell$. We apply our formalism to a few examples, in particular Myers-Perry black holes, black rings, and smooth multicentered geometries.
This short review is devoted to measures on infinite dimensional spaces. We start by discussing product measures and projective techniques. Special attention is paid to measures on linear spaces, and in particular to Gaussian measures. Transformation properties of measures are considered, as well as fundamental results concerning the support of the measure.
Effect of cold plasma on the form of rays propagating in the equatorial plane of a rotating black hole is investigated. Two kinds of regions in the radius-impact parameter plane allowed for the rays are constructed: for radiation with a given frequency at infinity and for radiation with a given ``telescope frequency'' seen by a local observer. The form of allowed regions for locally nonrotating observers as well as observers falling freely from infinity is established. The allowed regions contain rays which directly reach the horizon, or there exists a ``neck'' connecting the forbidden regions such that the rays coming from infinity cannot reach the horizon. In case we considered a set of observers at various radii instead of the neck we find two different regions -- from one the rays reach the horizon and not infinity and from the other one they reach infinity, but not the horizon. The results are analyzed by analytical methods and illustrated by figures constructed numerically.
In this study, we carry out a non-perturbative approach to a quantum Otto engine, employing an Unruh-DeWitt particle detector to extract work from a quantum Klein-Gordon field in an arbitrary globally hyperbolic curved spacetime. We broaden the scope by considering the field in any quasi-free state, which includes vacuum, thermal, and squeezed states. A key aspect of our method is the instantaneous interaction between the detector and the field, which enables a thorough non-perturbative analysis. We demonstrate that the detector can successfully extract positive work from the quantum Otto cycle, even when two isochoric processes occur instantaneously, provided the detector in the second isochoric process receives a signal from the first interaction. This signaling allows the detector to release heat into the field, thereby the thermodynamic cycle is completed. As a demonstration, we consider a detector at rest in flat spacetime and compute the work extracted from the Minkowski vacuum state.
We utilize three point amplitudes with (spinning) particles of unequal mass and a graviton to capture the dynamics of absorption processes. We demonstrate that the construction can represent the spheroidal harmonics appearing in the Teukolsky equations. The absolute square of the ``Wilson coefficients'' in this effective description can be fixed by matching to the known absorptive cross-sections. As an application, we compute corrections to the gravitational Compton amplitude from the exchange of states corresponding to such absorption effects. In the super-extremal limit, the corrections generate the non-analytic $|a|$-dependent contribution of the Compton amplitude found in ref.\cite{Bautista:2022wjf}.
Motivated by the recent work about the Extended Uncertainty Principle (EUP) black holes \cite{Mureika:2018gxl}, we present in this study its extension called the Generalized Extended Uncertainty Principle (GEUP) black holes. In particular, we investigated the GEUP effects on astrophysical and micro-black holes. First, we derive the expression for the shadow radius to investigate its behavior as perceived by a static observer located near and far from the black hole. Constraints to the large fundamental length scale $L*$ up to $2\sigma$ level were also found using the EHT data: for Sgr. A*, $L* = 5.716\text{x}10^{10}$ m, while for M87*, $L* = 3.264\text{x}10^{13}$ m. Under the GEUP effect, the value of the shadow radius behaves the same way as the Schwarzschild case due to a static observer, and the effect only emerges if the mass of the black hole $M$ is around the order of magnitude of $L_*$ (or $l_\text{Pl}$). In addition, the GEUP effect increases the shadow radius for astrophysical black holes, but the reverse happens for micro-black holes. We also explored GEUP effects to the weak and strong deflection angles as an alternative analysis. For both realms, a time-like particle gives a higher value for the weak deflection angle. Similar to the shadow, the deviation is seen when the values of $L_*$ and $M$ are close. The strong deflection angle gives more sensitivity to GEUP deviation at smaller masses in the astrophysical scenario. However, the weak deflection angle is a better probe in the micro world.
One of the key applications of AdS/CFT correspondence is the duality it dictates between the entanglement entropy of Anti-de Sitter (AdS) black holes and lower-dimensional conformal field theories (CFTs). Here we employ a square lattice of fermions with inhomogeneous tunneling couplings that simulate the effect rotationally symmetric 3D black holes have on Dirac fields. When applied to 3D BTZ black holes we identify the parametric regime where the theoretically predicted 2D CFT faithfully describes the black hole entanglement entropy. With the help of the universal simulator we further demonstrate that a large family of 3D black holes exhibit the same ground state entanglement entropy behavior as the BTZ black hole. The simplicity of our simulator enables direct numerical investigation of a wide variety of 3D black holes and the possibility to experimentally realize it with optical lattice technology.
We propose that the dynamics of Kerr black holes is strongly constrained by the principle of gauge symmetry. We initiate the construction of EFTs for Kerr black holes of any integer quantum spin s using Stueckelberg fields, and show that the known three-point Kerr amplitudes are uniquely predicted using massive higher-spin gauge symmetry. This symmetry is argued to be connected to an enhanced range of validity for the Kerr EFTs. We consider the closely related root-Kerr electromagnetic solution in parallel, for which the dynamical interactions with photons are also constrained by massive higher-spin gauge symmetry. Finally, the spin-s Compton amplitudes are analyzed, and we discuss contact-term constraints at s=2 from Ward identities.
We develop a Lagrangian quantization formalism for a class of theories obtained by the restriction of the configuration space of gauge fields from a wider (parental) gauge theory. This formalism is based on application of the Batalin-Vilkovisky technique for quantization of theories with linearly dependent generators, their linear dependence originating from a special type of projection from the originally irreducible gauge generators of the parental theory. The algebra of these projected generators is shown to be closed for parental gauge algebras closed off shell. We demonstrate that new physics of the restricted theory, as compared to its parental theory, is associated with the rank deficiency of a special gauge-restriction operator reflecting the gauge transformations of the restriction constraints functions -- this distinguishes the restricted theory from its partial gauge fixing. As a byproduct of this technique a workable algorithm for the one-loop effective action in generic first-stage reducible theory was constructed, along with the explicit set of tree-level Ward identities for gauge field, ghost, and ghosts-for-ghosts propagators. The formalism is applied to unimodular gravity theory, and its one-loop effective action is obtained in terms of functional determinants of minimal second-order operators, calculable on generic backgrounds by Schwinger-DeWitt technique of local curvature expansion. The result is shown to be equivalent to Einstein gravity theory with a cosmological term up to a special contribution of the global degree of freedom associated with the variable value of the cosmological constant. The role of this degree of freedom in a special duality relation between Einstein theory and unimodular gravity is briefly discussed.
A two scalar field model that incorporates non Riemannian Measures of integration or usually called Two Measures Theory (TMT) is introduced, in order to unify the early and present universe. In the Einstein frame a K-essence is generated and as a consequence for the early universe, we can have a Non Singular Emergent universe followed by Inflation and for the present universe dark epochs with consistent generation of dark energy (DE), dark matter (DM) and stiff matter. The scale invariance is introduced and then is spontaneously broken from the integration of the degrees of freedom associated with the modified measures. The resulting effective potentials and K-essence in the Einstein frame produce three flat regions corresponding to the different epochs mentioned before. For the first flat region we can associate an emergent and an inflationary universe. Here for a parameter-space region this flat plateau possesses a non singular stable emergent universe solution which characterizes an initial epoch of evolution that precedes the inflationary scenario. Also assuming this first plateau, we study the inflation in the framework of the slow-roll approximation. The corresponding cosmological perturbations in our model are determined and we also obtain the different constrains on the parameter-space from the Planck data.In the following flat region DE and also the DM, which does not need to be introduced separately, it is instead a result of a K-essence induced by the multi measures, multi field theory. Also stiff matter component is automatically generated from the K-essence theory from two scalar fields. From the perturbative analysis associated to the perturbation solution of background, we find a correlation between the two scalars. Besides, we obtain that our model during the dark epoch has a behavior of tracking freezing model.
During the glorious success of the EHT in providing the first image of a black hole, numerous papers have been published about the effect of different astrophysical environments on black hole geometry. Motivated by the work on how gravitational wave affects the shadow of a Schwarzschild black hole [Eur. Phys. J. C 10.1140/epjc/s10052-021-09287-2], we extend it by considering a quantum correction on the black hole through the extended uncertainty principle (EUP). Along with this correction, we probe the gravitational wave's effect on the null geodesics, and photonsphere, and find constraints to the gravitational wave parameter $\epsilon$ using the black hole shadow of M87* for some given test value for the gravitational wave frequency $\sigma$. Not only that some nodes were found in the light trajectory, but the general behavior of paths changes in a periodic way as the time $t$ progresses. These patterns then confirm the chaotic formation of the shadow seen by some remote observer. Finally, the constraint that we find for $\epsilon$ is $~10^{-10}$ orders of magnitude for the effect of the gravitational wave to be seen at a distance of $D = 16.8$ Mpc. As a consequence of such a value for $\epsilon$, another result reveals that while there is are gravitational wave effect on the shadow perceived at $D$, the deviations on the photonsphere are nearly non-existent. Apart from Earth-based detectors for gravitational waves, the study implies the possibility of an alternative detection method especially if a gravitational wave source is near a lone black hole.
We consider quantum algebras of observables associated with subregions in theories of Einstein gravity coupled to matter in the $G_N\rightarrow 0$ limit. When the subregion is spatially compact or encompasses an asymptotic boundary, we argue that the algebra is a type II von Neumann factor. To do so in the former case we introduce a model of an observer living in the region; in the latter, the ADM Hamiltonian effectively serves as an observer. In both cases the entropy of states on which this algebra acts is UV finite, and we find that it agrees, up to a state-independent constant, with the generalized entropy. For spatially compact regions the algebra is type II$_1$, implying the existence of an entropy maximizing state, which realizes a version of Jacobson's entanglement equilibrium hypothesis. The construction relies on the existence of well-motivated but conjectural states whose modular flow is geometric at an instant in time. Our results generalize the recent work of Chandrasekaran, Longo, Penington, and Witten on an algebra of operators for the static patch of de Sitter space.
We argue that the boundary of an asymptotically anti-de Sitter (AdS) space of dimension $d+1$, say $M^{d+1}$, can be locally reconstructed from a codimension-two defect located in the deep interior of a negatively curved Einstein manifold $X^{d+2}$ of one higher dimension. This means that there exist two different ways of thinking about the same $d$-submanifold, $\Sigma^d$: either as a defect embedded in the interior of $X^{d+2}$, or as the boundary of $M^{d+1}$ in a certain zero radius limit. Based on this idea and other geometric and symmetry arguments, we propose the existence of an infrared field theory on a bulk $\mathbb Z_n$-orbifold defect, located in the deepest point of the interior of AdS$^{d+2}$. We further conjecture that such a theory gives rise to the holographic theory at the asymptotic boundary of AdS$^{d+1}$, in the limit where the orbifold parameter $n\to\infty$. As an example, we compute a defect central charge when $\Sigma$ is a 2-manifold of fixed positive curvature, and show that its $n\to\infty$ limit reproduces the central charge of Brown and Henneaux.
Current searches for signals of departures from the fundamental symmetries of General Relativity using gravitational waves are largely dominated by propagation effects like dispersion and birefringence from highly dynamic sources such as coalescing binary-black holes and neutron stars. In this paper we take steps towards probing the nature of spacetime symmetries in the {\it generation-stage} of gravitational waves; by using a generic effective-field theory, we solve the modified Einstein equations order-by-order (in the coefficients for the symmetry breaking) for a generic source, and we write down the the first Post-Newtonian corrections, which includes contributions from the spacetime-symmetry breaking terms. Choosing as the source a system of point particles allows us to write down a simple toy solution explicitly, and we see that in contrast to General Relativity, the monopolar and dipolar contributions are non-vanishing. We comment on the detectability of such signals by the Laser Interferometer Space Antenna (LISA) space mission, which has high signal-to-noise galactic binaries (which can be modelled as point particles) well inside its predicted sensitivity band, sources which are inaccessible for current ground-based detectors, and we also discuss the possibility of going beyond the quadrupole formula and the first Post-Newtonian order, which would reveal effects which could be probed by ground-based detectors observing coalescence events.
Relativistic field theory for a vector field on a curved space-time is considered assuming that the Lagrangian field density is quadratic and contains field derivatives of first order at most. By applying standard variational calculus, the general Euler-Lagrange equations for the field are derived and the existence of a conserved current is achieved. The field equations are also analyzed from an eikonal-like point of view. The Hilbert energy-momentum tensor of the field is also derived and the influence of each one of the irreducible pieces appearing in the Lagrangian is studied. Particular values of the free parameters allow to retrieve known results.
Four spherically symmetric but non-asymptotically flat black hole solutions surrounded with spherical dark matter distribution perceived under the minimal length scale effect is derived via the generalized uncertainty principle. Here, the effect of this quantum correction, described by the parameter $\gamma$, is considered on a toy model galaxy with dark matter and the three well-known dark matter distributions: the cold dark matter, scalar field dark matter, and the universal rotation curve. The aim is to find constraints to $\gamma$ by applying these solutions to the known supermassive black holes: Sagittarius A (Sgr. A*) and Messier 87* (M87*), in conjunction with the available Event Horizon telescope. The effect of $\gamma$ is then examined on the event horizon, photonsphere, and shadow radii, where unique deviations from the Schwarzschild case are observed. As for the shadow radii, bounds are obtained for the values of $\gamma$ on each black hole solution at $3\sigma$ confidence level. The results revealed that under minimal length scale effect, black holes can give positive (larger shadow) and negative values (smaller shadow) of $\gamma$, which are supported indirectly by laboratory experiments and astrophysical or cosmological observations, respectively.
We investigate the interior of a dynamical black hole as described by the Einstein-Maxwell-charged-Klein-Gordon system of equations with a cosmological constant, under spherical symmetry. In particular, we consider a characteristic initial value problem where, on the outgoing initial hypersurface, interpreted as the event horizon $\mathcal{H}^+$ of a dynamical black hole, we prescribe: a) initial data asymptotically approaching a fixed sub-extremal Reissner-Nordstr\"om-de Sitter solution; b) an exponential Price law upper bound for the charged scalar field. After showing local well-posedness for the corresponding first-order system of partial differential equations, we establish the existence of a Cauchy horizon $\mathcal{CH}^+$ for the evolved spacetime, extending the bootstrap methods used in the case $\Lambda = 0$ by Van de Moortel. In this context, we show the existence of $C^0$ spacetime extensions beyond $\mathcal{CH}^+$. Moreover, if the scalar field decays at a sufficiently fast rate along $\mathcal{H}^+$, we show that the renormalized Hawking mass remains bounded for a large set of initial data. With respect to the analogous model concerning an uncharged and massless scalar field, we are able to extend the range of parameters for which mass inflation is prevented, up to the optimal threshold suggested by the linear analyses by Costa-Franzen and Hintz-Vasy. In this no-mass-inflation scenario, which includes near-extremal solutions, we further prove that the spacetime can be extended across the Cauchy horizon with continuous metric, Christoffel symbols in $L^2_{\text{loc}}$ and scalar field in $H^1_{\text{loc}}$. By generalizing the work by Costa-Gir\~ao-Nat\'ario-Silva to the case of a charged and massive scalar field, our results reveal a potential failure of the Christodoulou-Chru\'sciel version of the strong cosmic censorship under spherical symmetry.
Mimetic gravity is a modified theory of gravity which is able to incorporate dark matter into the underlying geometry of space-time by isolating the conformal degree of freedom. The theory has been studied extensively in the cosmological regime, as such, we set out to study the implications of the theory at astrophysical scales. To that end, we carry out the post-Newtonian expansion of mimetic gravity to lowest post-Newtonian order. We interpret the equations in the Newtonian limit and study some of the implications of the theory at the solar system scale. Then by establishing some bounds on the asymptotic behavior of the fields we prove that any static spherically symmetric space-time with a non trivial mimetic contribution cannot be asymptotically flat. Finally, we study static spherically symmetric solutions. To explain the rotation curves, one needs a logarithmic term in the potential, we show that even though the mimetic fluid can't reconstruct an exact logarithmic term, it is able to contribute a quasi-logarithmic term which recovers the basic qualitative features of galactic rotation curves.
Using the integration of wave equation in time-domain we show that scalar field perturbations around the $(2+1)$-dimensional asymptotically flat black hole with Gauss-Bonnet corrections is dynamically stable even for the near extreme values of the coupling constant.
In this study, we explore the black bounce solution in Rastall gravity and its potential source field, which can be described as a black hole or wormhole solution depending on certain parameters. We focus on the Bardeen-Type black bounce and Simpson-Visser solution and aim to identify an appropriate source field for these solutions. Our findings suggest that in Rastall gravity, a source for the black bounce solution with non-linear electromagnetic can be found. However, in the presence of a non-linear electromagnetic source, it is impossible to identify an appropriate source for the black bounce solution without a scalar field. We also investigate the energy conditions outside the event horizon for two types of black bounce solutions: Simpson-Visser and Bardeen. We find that these solutions do not satisfy the null energy condition, but we also reveal that Rastall gravity has more flexibility for maintaining some of the energy conditions by selecting an appropriate value for the Rastall parameter $\gamma$.
Adopting a general framework for quantum-classical dynamics, we analyze the interaction between quantum matter and a classical gravitational field. We point out that, assuming conservation of momentum or energy, and assuming that the dynamics obeys a particular decomposition property set out in the paper, the classical gravitational field cannot change the momentum or energy of the quantum system, whereas the quantum gravitational field can do so. Drawing upon the fundamental relationship between conservation laws and the quantum properties of objects, our analysis offers new perspectives for the study of quantum gravity and provides a novel interpretation of existing experimental observations, such as free fall.
Information located in an entanglement island in semiclassical gravity can be nonperturbatively reconstructed from distant radiation, implying a radical breakdown of effective field theory. We show that this occurs well outside of the black hole stretched horizon. We compute the island associated to large-angular momentum Hawking modes of a four-dimensional Schwarzschild black hole. These modes typically fall back into the black hole but can be extracted to infinity by relativistic strings or, more abstractly, by asymptotic boundary operators constructed using the timelike tube theorem. Remarkably, we find that their island can protrude a distance of order $\sqrt{\ell_p r_{\rm hor}}$ outside the horizon. This is parametrically larger than the Planck scale $\ell_p$ and is comparable to the Bohr radius for supermassive black holes. Therefore, in principle, a distant observer can determine experimentally whether the black hole information paradox is resolved by complementarity, or by a firewall.
In this paper, we determine a basis for the on-shell 4-point amplitudes $VVVV$ for Standard Model gauge bosons $V=W^\pm, Z, \gamma, g$. Following previous work, this completes the analysis of 3- and 4-point amplitudes for the Standard Model and could be used for model independent searches for beyond the Standard Model physics at colliders. Our results include a Lagrangian parametrization for the "primary" amplitudes, where including additional derivatives leads to the Mandelstam "descendant" amplitudes, and upper bounds on the coupling constants from imposing unitarity. We also perform an estimate for the sensitivity for new $Z$ decays at the HL-LHC, finding that $Z\to \gamma \bar{\ell}\ell$ could be searched for, but that other decay modes, like $Z\to (\gamma\gamma\gamma, \gamma gg)$, are too small to be discovered after imposing unitarity constraints.
We study a Lepton-Flavored Dark Matter model and its signatures at a future Muon Collider. We focus on the less-explored regime of feeble dark matter interactions, which suppresses the dangerous lepton-flavor violating processes, gives rise to dark matter freeze-in production, and leads to long-lived particle signatures at colliders. We find that the interplay of dark matter freeze-in and its mediator freeze-out gives rise to an upper bound of around TeV scales on the dark matter mass. The signatures of this model depend on the lifetime of the mediator, and can range from generic prompt decays to more exotic long-lived particle signals. In the prompt region, we calculate the signal yield, study useful kinematics cuts, and report tolerable systematics that would allow for a $5\sigma$ discovery. In the long-lived region, we calculate the number of charged tracks and displaced lepton signals of our model in different parts of the detector, and uncover kinematic features that can be used for background rejection. We show that, unlike in hadron colliders, multiple production channels contribute significantly which leads to sharply distinct kinematics for electroweakly-charged long-lived particle signals. Ultimately, the collider signatures of this lepton-flavored dark matter model are common amongst models of electroweak-charged new physics, rendering this model a useful and broadly applicable benchmark model for future Muon Collider studies that can help inform work on detector design and studies of systematics.
Axions are among the most sought-after candidates for dark matter. In the ultralight regime, they could help alleviate puzzles in small scale cosmology. Searches for a halo of axion dark matter rely on the electromagnetic response to a magnetic field. In this work, we resolve a number of issues in the determination of this response by carefully solving Maxwell's equations in the presence of an axion background. We find that the electric field induced by a magnetic field in an axion background is significant and unsuppressed by the size of the experiment.
Universal theories are a broad class of well-motivated microscopic dynamics of the electroweak sector that go beyond the Standard Model description. The long distance physics is described by electroweak parameters which correspond to local operators in the Effective Field Theory. We show how unitarity and analyticity constrain the space of parameters. In particular, the $W$ and $Y$ parameters are constrained to be positive and are necessarily the leading terms in the low energy expansion. We assess the impact of unitarity on the interpretation of Drell-Yan data. In passing, we uncover an unexpected Wilson coefficient transcendental cancellation at the $\mathcal{O}(<10^{-3})$ level.
We conduct a comprehensive study on the sub-GeV millicharge dark matter produced through the freeze-in mechanism. We discuss in general the mixing mechanism, encompassing both kinetic mixing and mass mixing, between the $U(1)_X$ hidden sector and the standard model, which can generate millicharge carried by the dark fermions from the hidden sector. We discuss in depth how such millicharge is generated, and clarify several misunderstandings regarding this subject in the literature. Without employing an effective field theory approach, where the photon field directly mixed with the additional $U(1)$, we analyze a general renormalizable model and investigate the complete evolution of the hidden sector particles precisely. Due to the substantial self-interactions among hidden sector particles, the evolution of the hidden sector temperature plays a crucial role, which is addressed concurrently with the number densities of hidden sector particles by solving a set of coupled Boltzmann equations. We thoroughly examine eight benchmark models covering six distinct cases. Some of our key findings from the analysis of these benchmark models may be generalizable and applicable to broader freeze-in scenarios. We also explore the possibility that the $\mathcal{O}$(keV) $U(1)_X$ dark photon is a viable dark matter candidate, even though it can contribute at most $\sim 5\%$ to the total observed dark matter relic density.
We examine simple models with an inert scalar and vector-like leptons that can explain the recent $g_{\mu}-2$ measurement reported at FNAL. Prompted by this exciting result, we explore the viability of a simple interpretation and determine the required parameters. We also embed these models within a 3-3-1 gauge extension of the Standard Model (SM), showing that the $g_{\mu}-2$ anomaly can be accommodated in agreement with current data. We also show how our theory can be tested at high-energy colliders such as HL-LHC and FCC-hh.
In this work we explore the phenomenological implications at future $e^+e^-$ colliders of assuming anomalous couplings of the Higgs boson to gauge bosons $HVV$ and $HHVV$ ($V=W,Z$) given by the $\kappa$-modifiers with respect to the Standard Model couplings, $\kappa_V$ and $\kappa_{2V}$, respectively. For this study we use the Higgs Effective Field Theory (HEFT) where these two $\kappa$ parameters are identified with the two most relevant effective couplings at leading order, concretely $a=\kappa_V$ and $b=\kappa_{2V}$. Our focus is put on these two couplings and their potential correlations which we believe carry interesting information on the underlying ultraviolet theory. The particular studied process is $e^+e^- \to HH \nu \bar \nu$, where the vector boson scattering subprocess $WW \to HH$ plays a central role, specially at the largest planned energy colliders. Our detailed study of this process as a function of the energy and the angular variables indicates that the produced Higgs bosons in the BSM scenarios will have in general a high transversality as compared to the SM case if $\kappa_V^2 \neq \kappa_{2V}$. In order to enhance the sensitivity to these HEFT parameters $\kappa_V$ and $\kappa_{2V}$ and their potential correlations we propose here some selected differential cross sections for the $e^+e^- \to HH \nu \bar\nu$ process where different kinematic properties of the BSM case with respect to the SM are manifested. Finally, we will focus on the dominant Higgs decays to $b \bar b$ pairs leading to final events with 4 $b$-jets and missing transverse energy from the undetected neutrinos and will provide the expected accessibility to the $(\kappa_V,\kappa_{2V})$ effective couplings and their potential correlations. In our study we will consider the three projected energies for $e^+e^-$ colliders of 500 GeV, 1000 GeV and 3000 GeV.
We study the near threshold behavior of cross sections of low-energy antiproton scattering off the ground and excited states of positronium with zero total orbital momentum $L=0$. In our computational experiment, the existence of singularities called the Gailitis-Damburg oscillations above the thresholds of excited states of positronium and antihydrogen atoms is confirmed. In the future the obtained results can be useful for developing proposals for improving the conditions of experiments with antimatter.
Spin-flip processes in the deep inelastic scatterings are thought to be suppressed in the high energy. Recent studies by Hatta and Zhou, however, show that gluon generalized parton distribution (GPD) $E_g$, which is associated with spin-flip processes, exhibits the Regge behavior identical to the BFKL Pomeron. This was done by deriving the small-$x$ evolution equation for the real part of $F$-type spin-flip gluon GTMDs $F_{1,2}$. In this article, we have shown that though the evolution equation for ${\rm Re}(F_{1,2})$ has IR poles - they all mutually cancel - making the equation IR finite and self-consistent. We also have analytically solved the equations in the dilute regime and find small-$x$ asymptotics of the GTMDs ${\rm Re}(F_{1,2})$ as \begin{eqnarray} {\rm Re}(F_{1,2}) \sim \left(\frac{1}{x}\right)^{\alpha_s\left(4\ln2-8/3\right)} \left(\cos 3\phi_{k\Delta} +\cos \phi_{k\Delta}\right). \nonumber \end{eqnarray} Interestingly, the surviving solution corresponds to conformal spin $n=2$ and carries an explicit $\cos 3\phi_{k\Delta} + \cos \phi_{k\Delta}$ azimuthal dependence. As the imaginary part of $F_{1,2}$, is related to the spin-dependent odderon or Gluon Siver function and scales as ${\rm Im}(F_{1,2}) \sim x^{0}$, the positive intercept for ${\rm Re}(F_{1,2})$, implies that it is expected to dominate over the gluon Siver function in the small-$x$ limit - and may directly impact the modeling of unpolarised GTMDs and associated spin-flip processes.
We calculate the exclusive $\mathrm{J}/\psi$ photoproduction cross section at high energies from the Color Glass Condensate approach. The results are compared to the center-of-mass energy dependent $\gamma+A\to\mathrm{J}/\psi+A$ cross sections extracted from measurements in ultra peripheral heavy ion collisions at RHIC and LHC. We predict strong saturation-driven nuclear suppression at high energies, while LHC data prefers even stronger suppression. We explore the effect of nucleon shape fluctuations on the nuclear suppression in the coherent and incoherent cross sections, and show that the most recent measurement of the $|t|$-differential incoherent $\mathrm{J}/\psi$ cross section prefers large event-by-event fluctuations of the nucleon substructure in heavy nuclei, comparable to that found for a free proton.
If the terrestrial environment is permeated by dark matter, the levitation experiences damping forces and fluctuations attributed to dark matter. This paper investigates levitodynamics with multiple stochastic forces, including thermal drag, photon recoil, feedback, etc., assuming that all of these forces adhere to the fluctuation-dissipation theorem. The ratio of total damping to the stochastic damping coefficient distinguishes the levitodynamics from cases involving only one single stochastic force. The heating and cooling processes are formulated to determine the limits of temperature change. All sources of stochastic forces are comprehensively examined, revealing that dark matter collisions cannot be treated analogously to fluid dynamics. Additionally, a meticulous analysis is presented, elucidating the intricate relationship between the fundamental transfer cross-section and the macroscopic transfer cross-section. While the dark damping coefficient is suppressed by the mass of the levitated particle, scattering can be coherently enhanced based on the scale of the component microscopic particle, the atomic form factor, and the static structure factor. Hence, dark damping holds the potential to provide valuable insights into the detection of the macroscopic strength of fundamental particles. We propose experimental procedures for levitation and employ linear estimation to extract the dark damping coefficient. Utilizing current levitation results, we demonstrate that the fundamental transfer cross section of dark matter can be of the order $\sigma^{\rm D}_{T}\lsim {\cal O}(10^{-26})\rm cm^2$.
The importance of the nonlinear corrections on the momentum sum rule is investigated on the initial scale $Q_{0}^2$. Nonlinear corrections are found to play an indispensable role in the singlet and gluon momentum sum rule in the high-order approximations in the parameterization groups for nucleons and light nuclei at low $x$ in future colliders. In this way, we obtain a significantly different low $x$ behavior of the singlet and gluon momentum sum rule at the hotspot point.
We simulate the space-time dynamics of high-energy collisions based on a microscopic kinetic description, in order to determine the range of applicability of an effective description in relativistic viscous hydrodynamics. We find that hydrodynamics provides a quantitatively accurate description of collective flow when the average inverse Reynolds number is sufficiently small and the early pre-equilibrium stage is properly accounted for. By determining the breakdown of hydrodynamics as a function of system size and energy, we find that it is quantitatively accurate in central lead-lead collisions at LHC energies, but should not be used in typical proton-lead or proton-proton collisions, where the development of collective flow cannot accurately be described within hydrodynamics.
We consider the fermion mass renormalization due to the vector boson exchange within mesodynamics with nucleon and $\rho$ meson fields as well as quantum electrodynamics with electron and photon fields. The method of unitary clothing transformations is used to handle the so-called clothed particle representation that allows us to get rid of mass counterterms directly in the Hamiltonian. Thus, they can no longer appear in the S-matrix. Special attention is paid to the cancellation of the so-called contact terms that are inevitable in models with vector bosons. Within this formalism, the second-order mass shifts are derived. They are expressed through the corresponding three-dimensional integrals whose integrands depend on certain covariant combinations of the relevant three-momenta. Our results are proved to be particle-momentum independent and compared with ones obtained by Feynman techniques.
The search for sub-GeV dark matter via scattering on electrons has ramped up in the last few years. Like in the case of dark matter scattering on nuclei, electron-recoil-based searches also face an ultimate background in the form of neutrinos. The so-called "neutrino fog'' refers to the range of open dark-matter parameter space where the background of neutrinos can potentially prevent a conclusive discovery claim of a dark matter signal from being made. In this study, we map the neutrino fog for a range of electron recoil experiments based on silicon, germanium, xenon and argon targets. In analogy to the nuclear recoil case, we also calculate the "edge'' to the neutrino fog, which can be used as a visual guide to where neutrinos become an important background -- this boundary excludes some parts of the key theory milestones used to motivate these experiments.
The TMD soft function can be obtained by formulating the Wilson line in terms of auxiliary 1-dimensional fermion fields on the lattice. In this formulation, the directional vector of the auxiliary field in Euclidean space has the form $\tilde n = (in^0, \vec 0_\perp, n^3)$, where the time component is purely imaginary. The components of these complex directional vectors in the Euclidean space can be mapped directly to the rapidities of the Minkowski space soft function. We present the results of the one-loop calculation of the Euclidean space analog to the soft function using these complex directional vectors. As a result, we show that the calculation is valid only when the directional vectors obey the relation: $|r| = |n^3/n^0| > 1$, and that this result corresponds to a computation in Minkowski space with space-like directed Wilson lines. Finally, we show that a lattice calculable object can be constructed that has the desired properties of the soft function.
The conjectured duality between color and kinematics has significantly advanced our understanding of both gauge and gravitational theories. However, constructing numerators that manifest the color-kinematics (CK) duality, even for the two-loop four-gluon amplitude in pure Yang-Mills, has been challenging. In this paper, we revisit this amplitude and show that the difficulty of applying CK duality can be overcome by introducing a simple deformation. Our approach distinguishes itself from previous studies by maximizing the use of off-shell CK duality while maintaining a compact ansatz. In particular, the deformation we introduce satisfies a subset of off-shell dual Jacobi relations. The resulting numerators are presented in $d$-dimensionally Lorentz invariant local form and are applicable to all helicities of external gluons. The solution we provide can be directly employed to construct the corresponding gravitational amplitude through double copy. Our findings suggest a novel and efficient strategy for constructing high-loop gauge and gravitational amplitudes using CK duality.
We investigate the production of spin-3/2 hyperon pairs, $\Omega^- \bar{\Omega}^+$, in electron-positron annihilation within the helicity amplitude formalism. A refined selection of helicity basis matrices is proposed to relate polarization expansion coefficients and spin density matrix elements and to illuminate their inherent physical interpretations and symmetrical properties. With a novel parametrization scheme of helicity amplitudes, we perform an analysis of polarization correlation coefficients for double-tag $\Omega^- \bar{\Omega}^+$ pairs. We present three sets of expressions to describe the decay of $\Omega^{-}$ hyperons, and further address the existing tension in the measurements of its decay parameters, particularly $\phi_{\Omega}$. The method and the framework developed in this paper can also be applied to studies of the production and decay mechanisms of other spin-3/2 particles.
In this work, we delve into the often-overlooked cosmological implications of spontaneous breaking of non-Abelian discrete groups, specifically focusing on the formation of domain walls in the case of $S_{4}$ flavor symmetry. In particular, we investigate three interesting breaking patterns of the $S_4$ group and study the structure of the domain walls in the broken phase for three possible residual symmetries. The presentation of domain walls in the case of multiple vacua is usually complicated, which therefore implies that most of the analyzes only approximate their presentation. Here, we propose a subtle way to represent the $S_{4}$ domain wall networks by presenting the vacua in each breaking pattern as vectors with their components corresponding to their coordinates in the flavon space. Then, through the properties of the obtained vectors, we find that the domain wall networks can be represented by Platonic or Archimedean solids where the vertices represent the degenerate vacua while the edges correspond to the domain walls that separate them. As an illustration, we propose a type-II seesaw model that is based on the $S_{4}$ flavor symmetry, and study its phenomenological implications on the neutrino sector. To solve the domain wall problem within this toy model, we consider an approach based on high-dimensional effective operators induced by gravity that explicitly break the structure of the induced vacua favoring one vacuum over the others.
The impact of Next-to-Leading Order (NLO) QCD corrections to the differential distributions of J/psi and Upsilon mesons produced inclusively in gamma-gamma collisions is discussed for the kinematical conditions of LEP II for DELPHI and at the future Circular Electron-Positron Collider (CEPC). We take into account all sizeable contributions at LO in v^2 in NRQCD factorisation: 1) pure QED process gamma + gamma -> J/psi(3S^1_1) + \gamma up to alpha^3 alpha_s, 2) single-resolved-photon contributions up to alpha_s^4, 3) gamma+gamma -> J/psi + c c-bar up to alpha^2 alpha_s and 4) gamma+gamma -> J/psi + ggg up to alpha^2 alpha_s^3. We will also discuss the pure QED process as a contribution to the exclusive production in ultra-peripheral heavy-ion collisions (UPC) at the LHC.
Motivated by the LHCb Collaboration's observation of a doubly charmed tetraquark state $T_{cc}(3875)$, we systematically investigate the existence of doubly charmed pentaquark states using the resonating group method based on the QDCSM framework. The effective potential of the two involved hadrons and the bound state dynamics are included in the present work. Moreover, we have also calculated the scattering phase shifts of open channels by channel coupling to look for possible resonance states. Our estimations indicate that there is a bound state in $I(J^{P})=\frac{3}{2}(\frac{5}{2}^{-})$, with a mass of $4461.7$ MeV. Additionally, five resonance states can be obtained by coupling the open channel, which are $\Xi_{cc}\rho$ and $\Sigma_{c}D^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{1}{2}^{-})$, $\Lambda_{c}D^{\ast}$ and $\Sigma_{c}D^{\ast}$ with $I(J^{P})=\frac{1}{2}(\frac{3}{2}^{-})$ and $\Sigma_{c}D^{\ast}$ with $I(J^{P})=\frac{3}{2}(\frac{1}{2}^{-})$respectively. The existence of these predicted doubly charmed pentaquark states needs to be supported by experimental measurements and discoveries. We hope that some experiments can find evidence of these states.
We derive an explicit expression for the Lellouch-L\"uscher (LL) factor in the $K\to 3\pi$ decays at leading order (without derivative couplings). Several important technical details are addressed, like a proper decomposition into the isospin amplitudes, the choice of a minimal set of effective couplings and the renormalization, as well as the algorithm for the solution of the pertinent Faddeev equations in the infinite volume which is based on the contour deformation method. Most importantly, our numerical results demonstrate that the three-body force contributes very little to the LL factor. This result paves the way for the study of the $K\to 3\pi$ decays on the lattice.
We investigate the parameter space of the minimal inverse seesaw ISS(2,2) model for successful leptogenesis. The framework of ISS(2, 2) is realized by augmenting the Standard Model with two right-handed and two Standard Model singlet neutrinos. The decay of the heavy sterile states which is essentially an admixture of the right-handed and SM singlet neutrino states produces the baryon asymmetry of the universe. In this predictive model of leptogenesis, we study resonant leptogenesis where the mass splitting between the heavy sterile states is naturally achieved. We review the possibility of generating the observed baryon asymmetry of the universe via leptogenesis where the CP violation comes solely from the low-energy CP phases. In addition, we study the effect of texture zero in the Dirac mass matrix on the parameter space of the model for successful resonant leptogenesis.
We consider the Schwinger production of baryons in an external electric field in the worldline instanton approach. The process occurs in the confinement regime hence the holographic QCD and the Chiral Lagrangian are used as the tools. The new exponentially suppressed processes in a constant electric field involving the composite worldline instantons are suggested. These include the non-perturbative decay of a neutron into a proton and charged meson and the spontaneous production of $p\bar{n}\pi^{-}$ and $n\bar{p}\pi^{+}$ states.
We investigate the effect of gluon Bose enhancement in the nuclear wave function on the dijet production in incoherent diffractive processes in DIS and ultraperipheral collisions. We demonstrate that Bose enhancement leads to an enhancement of diffractive dijet production cross section when the transverse momenta of the two jets are aligned at zero relative angle. This enhancement is maximal when the magnitude of the transverse momenta of the two jets are equal, and disappears rather quickly as a function of the ratio of the two momenta. We study both the dilute limit and fully nonlinear dense regime where the nuclear wave function is evolved with the leading order JIMWLK equation. In both cases we observe a visible effect, with it being enhanced by the evolution due to the dynamical generation of the color neutralization scale.
We present all two-loop five-parton leading-colour finite remainders in the spinor-helicity formalism by analysing numerical evaluations of their known expressions in terms of Mandelstam invariants. Recasting them in terms of spinor-helicity variables allows us to obtain expressions which are more compact, faster to evaluate, numerically more stable and manifestly free from poles of higher order than necessary. At the same time, due to the better scaling of our reconstruction strategy with the complexity of the input, we required one order of magnitude fewer numerical samples to complete the analytical reconstruction than were needed by the authors of Ref. \cite{Abreu:2019odu}, albeit using higher numerical working precision. This places our reconstruction technique as an alternative to the finite-field single-numerator reconstruction for future applications.
In the last decades, the Standard Model (SM) of particle physics has been extensively tested and confirmed, with the announced discovery of the Higgs boson in 2012 being the last missing puzzle piece. Even though since then the search for new particles and interactions has been further intensified, the experiments ATLAS and CMS at the Large Hadron Collider (LHC) at CERN did not find evidence for the direct production of a new state. However, in recent years deviations between LHC data and SM predictions in multiple observables involving two or more leptons (electrons or muons) have emerged, the so-called ``multi-lepton anomalies'', pointing towards the existence of a beyond the SM Higgs boson $S$. While from these measurements its mass cannot be exactly determined, it is estimated to lay in the range between $130\,$GeV and $160\,$GeV. Motivated by this observation, we perform a search for signatures of $S$, by using existing CMS and ATLAS analyses. Combining channels involving the associate productions of SM gauge bosons ($\gamma\gamma$ and $Z\gamma$), we find that a simplified model with a new scalar with $m_S= 151.5\,$GeV is preferred over the SM hypothesis by 4.3$\sigma$ (3.9$\sigma$) locally (globally). On the face of it, this provides a good indication for the existence of a new scalar resonance $S$ decaying into photons, in association with missing energy and allows for a connection to the long-standing problem of Dark Matter. Furthermore, because $S$ is always produced together with other particles, we postulate the existence of a second new (heavier) Higgs boson $H$ that decays into $S$ and propose novel searches to discover this particle, which can be performed by ATLAS and CMS.
Ultralight bosonic dark matter has come under increasing scrutiny as a dark matter candidate that has the potential to resolve puzzles in astronomical observation. We demonstrate that high-precision measurements of time variation in the frequency ratios of atomic transitions achieves leading sensitivity to ultralight axion-like particle dark matter at low masses. These bounds are the first laboratory-based bounds on this class of dark matter models. We propose further measurements that could enhance sensitivity to ultralight axion-like particles.
Current quantum systems have significant limitations affecting the processing of large datasets with high dimensionality, typical of high energy physics. In the present paper, feature and data prototype selection techniques were studied to tackle this challenge. A grid search was performed and quantum machine learning models were trained and benchmarked against classical shallow machine learning methods, trained both in the reduced and the complete datasets. The performance of the quantum algorithms was found to be comparable to the classical ones, even when using large datasets. Sequential Backward Selection and Principal Component Analysis techniques were used for feature's selection and while the former can produce the better quantum machine learning models in specific cases, it is more unstable. Additionally, we show that such variability in the results is caused by the use of discrete variables, highlighting the suitability of Principal Component analysis transformed data for quantum machine learning applications in the high energy physics context.
Heavy-ion collisions can be well described through relativistic viscous hydrodynamics, but questions still remain when hydrodynamics is applicable because the initial state may begin very far-from-equilibrium. Thus, a pre-equilibrium evolution phase is used to bridge the gap between the initial state and hydrodynamics. K$\phi$MP$\phi$ST is one such pre-equilibrium model that propagates the energy-momentum tensor by decomposing it into the background and fluctuations around that background, whose evolution is captured by Green's functions. We extend this formalism to include conserved charges and calculate the corresponding non-equilibrium Green's functions in the relaxation time approximation. The ICCING algorithm initializes conserved charges in the initial state by sampling $g \rightarrow q\bar{q}$ splitting probabilities and is, thus, perfectly positioned to implement Green's functions for charge propagation. We show that this method alters the initial state charge geometries and is applicable in central to mid-central collisions.
Effects of non-linear small-x evolution of the gluon distribution given by the Balitsky-Kovchegov equation are analyzed within the collinear approximation framework. We perform a twist decomposition of the proton structure functions F2 and FL obtained from the Balitsky-Kovchegov equation using the Mellin representation of the scattering cross-sections at high energies. In both the structure functions we find strong corrections coming from the non-linear effects in the gluon evolution at twist 2, and strongly suppressed higher twist effects. This implies that unitarization effects of high energy scattering amplitudes are mostly the leading twist effect. Furthermore we consider the double logarithmic limit of the Balitsky--Kovchegov equation for the collinear gluon distribution, and compare the result to the Gribov-Levin-Ryskin equation. We find that these two equations differ by two powers of the hard scale logarithm for the large scales.
Kinetic and chemical equilibrations play important roles in the formation of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions (HICs). These processes further influence the production of hard and electromagnetic probes in HICs, in particular, the thermalization of heavy quarks, which are produced at an extremely early time before the formation of the QGP. We calculate the drag and diffusion coefficients of heavy quarks in the pre-hydrodynamic quantum chromodynamic (QCD) plasma with the state-of-the-art QCD effective kinetic theory (EKT) solver. We present the time, momentum, and angular dependencies of these coefficients for gluon and quark contributions separately, showing the effects of isotropization and chemical equilibration from the QCD plasma. We also provide a simple formula to estimate the heavy quark drag and diffusion coefficients, as well as its energy loss, within the pre-hydrodynamic plasma at different coupling strengths based on the attractor theory. We then discuss the validity of these estimations with leading-order calculations and leading-logarithmic rescaling factors.
The production of a top-antitop quark pair in association with a $W$ boson ($t\bar tW$) is one of the heaviest signatures currently probed at the Large Hadron Collider (LHC). Since the first observation reported in 2015 the corresponding rates have been found to be consistently higher than the Standard Model predictions, which are based on next-to-leading order~(NLO) calculations in the QCD and electroweak (EW) interactions. We present the first next-to-next-to-leading order (NNLO) QCD computation of $t\bar tW$ production at hadron colliders. The calculation is exact, except for the finite part of the two-loop virtual corrections, which is estimated using two different approaches that lead to consistent results within their uncertainties. We combine the newly computed NNLO QCD corrections with the complete NLO QCD+EW results, thus obtaining the most advanced perturbative prediction available to date for the \ttW inclusive cross section. The tension with the latest ATLAS and CMS results remains at the $1\sigma-2\sigma$ level.
Tachyon condensation in quantum field theory (QFT) plays a central role in models of fundamental interactions and cosmology. Inspired by tower truncation in string field theory, ultraviolet completions were proposed with infinite-derivative form factors that preclude the appearance of pathological ghosts in the particle spectrum, contrary to other local higher-derivative QFT's. However, if the infinite-derivative QFT exhibits other vacua, each of them has its own spectrum, which is generally not ghost-free: an infinite tower of ghost-like resonances pops up above the nonlocal scale at tree-level, whose consistency is unclear. In this article, a new weakly nonlocal deformation of a generic local QFT is introduced via a Lorentz and gauge covariant star-product of fields, which is commutative but nonassociative in general. This framework realizes tachyon condensation without ghosts at the perturbative level, with applications for spontaneous symmetry breaking.
The flexible method of reduction to finite integrals, briefly described in earlier publications of the author, is described in detail. The method is suitable for the calculation of all quantum electrodynamical contributions to the magnetic moments of leptons. It includes mass-dependent contributions. The method removes all divergences (UV, IR and mixed) point-by-point in Feynman parametric space without any usage of limit-like regularizations. It yields a finite integral for each individual Feynman graph. The subtraction procedure is based on the use of linear operators applied to the Feynman amplitudes of UV-divergent subgraphs; a placement of all terms in the same Feynman parametric space is implied. The final result is simply the sum of the individual graph contributions; no residual renormalization is required. The method also allows us to split the total contribution into the contributions of small gauge-invariant classes. The procedure offers a great freedom in the choice of the linear operators. This freedom can be used for improving the computation speed and for a reliability check. The mechanism of divergence elimination is explained, as well as the equivalence of the method and the on-shell renormalization. For illustrative purposes, all 4-loop contributions to the anomalous magnetic moments of the electron and muon are given for each small gauge-invariant class, as well as their comparison with previously known results. This also includes the contributions that depend on the ratios of the tau-lepton mass to the electron and muon mass.
The anomalous dimension of the heavy-light quark current in HQET is calculated up to four loops. The N$^3$LL perturbative correction to $f_B/f_D$ is obtained.
We report on a novel application of computer vision techniques to extract beyond the Standard Model (BSM) parameters directly from high energy physics (HEP) flavor data. We develop a method of transforming angular and kinematic distributions into "quasi-images" that can be used to train a convolutional neural network to perform regression tasks, similar to fitting. This contrasts with the usual classification functions performed using ML/AI in HEP. As a proof-of-concept, we train a 34-layer Residual Neural Network to regress on these images and determine the Wilson Coefficient $C_{9}$ in MC (Monte Carlo) simulations of $B \rightarrow K^{*}\mu^{+}\mu^{-}$ decays. The technique described here can be generalized and may find applicability across various HEP experiments and elsewhere.
The axion is an hypothetical beyond the Standard Model particle. Its experimental search is an ongoing effort, and an expanding number of techniques keep on narrowing its parameters space. Leveraging the interaction between dark matter axions and spins, a fermionic interferometer is an experiment which aims at detecting the axion-induced precession of a spin resonance. We describe the detection scheme, outline the possible experimental implementations, their sensitive axion-mass range and discovery potential. Furthermore, the building and characterisation of an axion interferometer is explained in details and the resulting setup is used to search for sub-neV dark matter.
New pseudoscalars, axion-like particles (ALPs), provide the exciting target for present and future collider-based experiments. Search for ALPs is performed in this paper via the $W^{+}W^{-}$ fusion process $e^{-}e^{+}\rightarrow\nu_{e}\overline{\nu_{e}}a\rightarrow\nu_{e}\overline{\nu_{e}}f\overline{f}$ at the $1$ TeV ILC corresponding to an integrated luminosity of $1$ ab$^{-1}$ and the beam polarization $P(e^{-}$, $e^{+}) = (-80\%$, $+20\%)$. Owing to the good capability of the ILC in performing b-tagging and the sufficiently large branching ratio of the ALP decaying into a pair of b quarks, the decay channel $a\rightarrow{b\overline{b}}$ is mainly concerned. The prospective sensitivities provided by the ILC on the ALP-fermion coupling as low as $1$ TeV$^{-1}$ and $1.75$ TeV$^{-1}$ are derived at $95\%$ confidence level in the ALP mass intervals $37-50$ GeV and $52-300$ GeV, respectively. Our results will help to probe significant parameter space in an unexplored region beyond the existing constraints.
We present DarkCLR, a novel framework for detecting semi-visible jets at the LHC. DarkCLR uses a self-supervised contrastive-learning approach to create observables that are approximately invariant under relevant transformations. We use background-enhanced data to create a sensitive representation and evaluate the representations using a normalized autoencoder as a density estimator. Our results show a remarkable sensitivity for a wide range of semi-visible jets and are more robust than a supervised classifier trained on a specific signal.
We study four-dimensional $\mathcal N=2$ superconformal circular, cyclic symmetric quiver theories which are planar equivalent to $\mathcal N=4$ super Yang-Mills. We use localization to compute nonplanar corrections to the free energy and the circular half-BPS Wilson loop in these theories for an arbitrary number of nodes, and examine their behaviour in the limit of long quivers. Exploiting the relationship between the localization quiver matrix integrals and an integrable Bessel operator, we find a closed-form expression for the leading nonplanar correction to both observables in the limit when the number of nodes and 't Hooft coupling become large. We demonstrate that it has different asymptotic behaviour depending on how the two parameters are compared, and interpret this behaviour in terms of properties of a lattice model defined on the quiver diagram.
Quantum chaotic systems are conjectured to display a spectrum whose fine-grained features (gaps and correlations) are well described by Random Matrix Theory (RMT). We propose and develop a complementary version of this conjecture: quantum chaotic systems display a Lanczos spectrum whose local means and covariances are well described by RMT. To support this proposal, we first demonstrate its validity in examples of chaotic and integrable systems. We then show that for Haar-random initial states in RMTs the mean and covariance of the Lanczos spectrum suffices to produce the full long time behavior of general survival probabilities including the spectral form factor, as well as the spread complexity. In addition, for initial states with continuous overlap with energy eigenstates, we analytically find the long time averages of the probabilities of Krylov basis elements in terms of the mean Lanczos spectrum. This analysis suggests a notion of eigenstate complexity, the statistics of which differentiate integrable systems and classes of quantum chaos. Finally, we clarify the relation between spread complexity and the universality classes of RMT by exploring various values of the Dyson index and Poisson distributed spectra.
Effective string theory has shown its universal power in the prediction of the spectrum of low-lying excited states of confining strings. Here we study confining flux tubes in $\mathbb{Z}_N$ gauge theories. For the $N=2$ theory, which corresponds to the 3d Ising gauge model, we compute the spectrum of low-lying excitations of confining strings and show that it agrees with the universal Nambu--Goto predictions except for an additional massive scalar resonance. This resonance, however, turns out to be a bulk glueball mixing with the flux tube excitations rather than a genuine string worldsheet state. In general $\mathbb{Z}_N$ gauge theories (dual to clock spin models), we observe a continuous phase transition for $N \geq 4$, while for $N > 5$ it is governed by the $O(2)$ universality class. The critical behavior of the string tension and mass gap is verified to be described by a dangerously irrelevant operator. At large $N$ the glueball spectrum is expected to approach the spectrum of U(1) gauge theory, which is confirmed by our lattice data.
We set up a hydrodynamic description of the non-equilibrium dynamics of sine-Gordon quantum field theory for generic coupling. It is built upon an explicit form of the Bethe Ansatz description of general thermodynamic states, with the structure of the resulting coupled integral equations encoded in terms of graphical diagrams. The resulting framework is applied to derive results for the Drude weights of charge and energy. Quantities associated with the charge universally have fractal dependence on the coupling, which is notably absent from those associated with energy, a feature explained by the different roles played by reflective scattering in transporting these quantities. We then present far-from-equilibrium results, including explicit time evolution starting from bipartite initial states and dynamical correlation functions. Our framework can be applied to explore numerous other aspects of non-equilibrium dynamics, which opens the way to a wide array of theoretical studies and potential novel experimental predictions.
The phenomenon of unpaired Weyl fermions appearing on the sole 2n-dimensional boundary of a (2n + 1)-dimensional manifold with massive Dirac fermions was recently analyzed recently. In this Letter we show that similar unpaired Weyl edge states can be seen on a finite lattice. In particular, we consider the discretized Hamiltonian for a Wilson fermion in (2+1) dimensions with a 1+1 dimensional boundary and continuous time. We demonstrate that the low lying boundary spectrum is indeed Weyl-like: it has a linear dispersion relation, definite chirality, and circulates only in one direction around the boundary. We comment on how our results are consistent with Nielsen-Ninomiya theorem. This work removes one potential obstacle facing the program recently outlined by one of the authors for regulating chiral gauge theories.
We show via explicit construction that all the extreme rays of both the 3-party quantum entropy cone and the 4-party stabilizer entropy cone can be obtained from subsystem coarse-grainings of specific higher-party quantum states, namely extreme states characterized by saturating a (non-trivial) maximal set of instances of subadditivity. This suggests that the study of the ``subadditivity cone'', and the set of its extreme rays realizable in quantum mechanics, provides a powerful new tool for deriving inner bounds for the quantum and stabilizer entropy cones, as well as constraints on new inequalities for the von Neumann entropy.
Equations of fluid mechanics with N=1 Schrodinger supersymmetry are formulated within the method of nonlinear realizations of Lie groups.
The double-scaled infinite temperature limit of the SYK model has been conjectured by Rahman and Susskind (RS) [1, 2, 3, 4], and independently by Verlinde [5] to be dual to a certain low dimensional de Sitter space. In a recent discussion of this conjecture Narovlansky and Verlinde (NV) [6] came to conclusions which radically differ from those of RS. In particular these conclusions disagree by factors which diverge as $N \to \infty$. Among these is a mismatch between the scaling of boundary entropy and bulk horizon area. In this note, we point out differences in two key assumptions made by RS and NV which lead to these mismatches, and explain why we think the RS assumptions are correct. When the NV assumptions, which we believe are unwarranted, are replaced by those of RS, the conclusions match both RS and the standard relation between entropy and area. In the process of discussing these, we will shed some light on: the various notions of temperature that appear in the duality; the relationship between Hamiltonian energy and bulk mass; and the location of bulk conical defect states in the spectrum of DSSYK$_{\infty}$.
Partially motivated by the fact that the grand partition function of the ABJM theory or its generalization is expressed by a spectral operator enjoying symmetries of the Weyl group, it was found that the grand partition function satisfies the q-Painleve equation, which is constructed from the affine Weyl group. In this paper we clarify the affine symmetries of the grand partition function. With the affine symmetries, we find that the grand partition function extends naturally outside the fundamental domain of duality cascades and once the Painleve equation holds in the fundamental domain, so does it outside.
Extending the results of \cite{Wu}, we study the double-scaling limit SYK (DSSYK) model with an additional diagonal matrix with a fixed number $c$ of nonzero constant entries $\theta$. This constant diagonal term can be rewritten in terms of Majorana fermion products. Its specific formula depends on the value of $c$. We find exact expressions for the moments of this model. More importantly, by proposing a moment-cumulant relation, we reinterpret the effect of introducing a constant term in the context of non-commutative probability theory. This gives rise to a $\tilde{q}$ dependent mixture of independences within the moment formula. The parameter $\tilde{q}$, derived from the q-Ornstein-Uhlenbeck (q-OU) process, controls this transformation. It interpolates between classical independence ($\tilde{q}=1$) and Boolean independence ($\tilde{q}=0$). The underlying combinatorial structures of this model provide the non-commutative probability connections. Additionally, we explore the potential relation between these connections and their gravitational path integral counterparts.
Motivated by recent parity violating electron scattering experiments, we compute the Neutron Skin Thickness (NST) of nuclei modelled as (quantized) Skyrmions, the topological solitons of the Skyrme model. We show how in a certain approximation, the result for the NST is oblivious to the fine details of the (generally very complicated) quantum state of the soliton and only depends on the total baryon number and the isospin number. Moreover, in the leading order, the linear dependence on the asymmetry parameter is recovered, as expected both from experimental data and other models of nuclei such as the liquid drop model.
We investigate the impact of measuring one subsystem on the holographic complexity of another. While a naive expectation might suggest a reduction in complexity due to the collapse of the state to a trivial product state during quantum measurements, our findings reveal a counterintuitive result: in numerous scenarios, measurements on one subsystem can amplify the complexity of another. We first present a counting argument elucidating this complexity transition in random states. Then, employing the subregion "complexity=volume" (CV) proposal, we identify a complexity phase transition induced by projection measurements in various holographic CFT setups, including CFT vacuum states, thermofield double states, and the joint system of a black hole coupled to a bath. According to the AdS/BCFT correspondence, the post-measurement dual geometry involves an end-of-the-world brane created by the projection measurement. The complexity phase transition corresponds to the transition of the entanglement wedge to the one connected to the brane. In the context of the thermofield double setup, complete projection on one side can transform the other side into a boundary state black hole with higher complexity or a pure AdS with lower complexity. In the joint system of a black hole coupled to a nongraviting bath, where (a part of) the radiation is measured, the BCFT features two boundaries: one for the black hole and the other for the measurement. We construct the bulk dual involving intersecting or non-intersecting branes, and investigate the complexity transition induced by the projection measurement. Notably, for a subsystem that contains the black hole brane, its RT surface may undergo a transition, giving rise to a complexity jump.
We introduce a reversible theory of exact entanglement manipulation by establishing a necessary and sufficient condition for state transfer under trace-preserving transformations that completely preserve the positivity of partial transpose (PPT). Under these free transformations, we show that logarithmic negativity emerges as the pivotal entanglement measure for determining entangled states' transformations, analogous to the role of entropy in the second law of thermodynamics. Previous results have proven that entanglement is irreversible under quantum operations that completely preserve PPT and leave open the question of reversibility for quantum operations that do not generate entanglement asymptotically. However, we find that going beyond the complete positivity constraint imposed by standard quantum mechanics enables a reversible theory of exact entanglement manipulation, which may suggest a potential incompatibility between the reversibility of entanglement and the fundamental principles of quantum mechanics.
Generalised Complex Geometry provides a natural interpretation of the $\mathcal{N}=1$ supersymmetry conditions for warped solutions of type II supergravity as differential equations on polyforms on the internal manifold. Written in this language the supersymmetry conditions correspond to calibration conditions for probe D-branes: D-string, domain-wall or space-filling branes, depending on the directions they span in the non-compact four-dimensional space. The BPS condition corresponding to the calibration of space-filling D-branes has been reformulated by Tomasiello, eliminating the explicit dependence on the metric. We generalise this derivation to the case of non-supersymmetric backgrounds violating the domain-wall and D-string calibration conditions. We use this reformulation to derive constraints that the ten-dimensional solutions with BPS space-filling sources must respect in order to dimensionally reduce to solutions of four-dimensional $\mathcal{N}=1$ supergravity with non-vanishing F-terms and potentially non-vanishing D-terms. We give the equations of motion for the class of type II vacua satisfying these constraints in the language of pure spinors. We investigate how restrictive these constraints are for the class of type IIB SU$(3)$ backgrounds with BPS space-filling O5-planes.
We propose commuting set of matrix-valued difference operators in terms of trigonometric ${\rm GL}(N|M)$-valued $R$-matrices providing quantum supersymmetric (and possibly anisotropic) spin Ruijsenaars-Macdonald operators. Two types of trigonometric supersymmetric $R$-matrices are used. The first is the one related to the affine quantized algebra ${\hat{\mathcal U}}_q({\rm gl}(N|M))$. The second is a graded version of the standard $\mathbb Z_n$-invariant $A_{n-1}$ type $R$-matrix. We show that being properly normalized the latter graded $R$-matrix satisfies the associative Yang-Baxter equation. Next, we proceed to construction of long-range spin chains using the Polychronakos freezing trick. As a result we obtain a new family of spin chains, which extend the ${\rm gl}(N|M)$-invariant Haldane-Shastry spin chain to q-deformed case with possible presence of anisotropy.
We consider ${\mathcal N}=1$ superconformal field theories in four dimensions possessing an additional conserved spinor current multiplet $S_{\alpha}$ and study three-point functions involving such an operator. A conserved spinor current multiplet naturally exists in superconformal theories with ${\mathcal N}=2$ supersymmetry and contains the current of the second supersymmetry. However, we do not assume ${\mathcal N}=2$ supersymmetry. We show that the three-point function of two spinor current multiplets and the ${\mathcal N}=1$ supercurrent depends on three independent tensor structures and, in general, is not contained in the three-point function of the ${\mathcal N}=2$ supercurrent. It then follows, based on symmetry considerations only, that the existence of one more Grassmann odd current multiplet in ${\mathcal N}=1$ superconformal field theory does not necessarily imply ${\mathcal N}=2$ superconformal symmetry.
What does it mean for a boundary condition to be symmetric with respect to a non-invertible global symmetry? We discuss two possible definitions in 1+1d. On the one hand, we call a boundary weakly symmetric if the symmetry defects can terminate topologically on it, leading to conserved operators for the Hamiltonian on an interval (in the open string channel). On the other hand, we call a boundary strongly symmetric if the corresponding boundary state is an eigenstate of the symmetry operators (in the closed string channel). These two notions of symmetric boundaries are equivalent for invertible symmetries, but bifurcate for non-invertible symmetries. We discuss the relation to anomalies, where we observe that it is sometimes possible to gauge a non-invertible symmetry in a generalized sense even though it is incompatible with a trivially gapped phase. The analysis of symmetric boundaries further leads to constraints on bulk and boundary renormalization group flows. In 2+1d, we study the action of non-invertible condensation defects on the boundaries of $U(1)$ gauge theory and several TQFTs. Starting from the Dirichlet boundary of free Maxwell theory, the non-invertible symmetries generate infinitely many boundary conditions that are neither Dirichlet nor Neumann.
This paper presents an evaluation of the wave function coefficients for conformally coupled scalars at both one and two-loop levels at leading order in the coupling constant, in momentum space. We take cues from time-dependent interactions in flat spacetime and under suitable approximations, these can also be used to study the wave function coefficients for general cosmologies. We make use of recursion relations developed in arxiv:\{1709.02813\} to regularize certain bulk-point integrals and express the wave function coefficients in a form that simplifies the loop integrals. We utilize hard-cutoff regularization to regularize the loop integrals and further provide a discussion on their renormalization. Our results can also be analytically continued to obtain answers for transition amplitudes in AdS.
The renormalization group equations of massive $\mathcal{N}=1$ supersymmetric quantum electrodynamics (SQED) are studied using the functional renormalization group approach. A non-perturbative form of the beta function has been computed via a derivative expansion of the effective action. In the local potential approximation, the functional form of the non-perturbative beta function is closely related to the form of the NSVZ exact beta function; this relationship is exact if an effective fine-structure constant is defined. The non-massive limit of the same is also analyzed. Furthermore, the calculation of the beta function has been improved by incorporating the influence of momentum modes on the propagation of the superfields in the non-perturbative running of the electric charge, applying a second-order truncation for the derivative expansion, which we use to find the momentum contributions to the $\beta$ function. Again, we find the NSVZ relation for an effective fine-structure constant.
In the context of $N =1$ four-dimensional type IIB supergravity theories, the U-dual completion arguments suggest to include four S-dual pairs of fluxes in the holomorphic superpotential, namely the so-called $(F, \, H), \, (Q, \, P), \, (P^\prime, Q^\prime)$ and $(H^\prime, \, F^\prime)$. These can generically induce cubic polynomials for the complex-structure moduli as well as the K\"ahler-moduli in the flux superpotential. In this article, we explore the insights of the four-dimensional non-geometric scalar potential in the presence of such generalized U-dual fluxes by considering an explicit type IIB toroidal compactification model based on an orientifold of ${\mathbb T}^6/({\mathbb Z}_2 \times {\mathbb Z}_2)$ orbifold. First, we observe that the flux superpotential induces a huge scalar potential having a total of 76276 terms involving 128 flux parameters and 14 real scalars. Subsequently, we invoke a new set of (the so-called) ``axionic fluxes" comprising combinations of the standard fluxes and the RR axions, and it turns out that these axionic fluxes can be very useful in rewriting the scalar potential in a relatively compact form. In this regard, using the metric of the compactifying toroidal sixfold, we present a new formulation of the effective scalar potential, which might be useful for understanding the higher-dimensional origin of the various pieces via the so-called ``dimensional oxidation" process. We also discuss the generalized Bianchi identities and the tadpole cancellation conditions, which can be important while seeking the physical (AdS/dS) vacua in such models.
In Type IIB flux compactification realizing the metastable de Sitter (dS) vacuum, the uplift potential can be generated by $\overline{\rm D3}$-branes at the tip of Klebanov-Strassler throat. Then the uplift potential obeys the scaling law with respect to the tower mass scale $m_{\rm sc}$, which can be the Kaluza-Klein (KK) mass scale associated with the throat containing $\overline{\rm D3}$-branes or the bulk tower mass scales, depending on the warping of the throat. On the other hand, in the presence of another throat of stronger warping, the KK mass scale associated with this throat is lower than $m_{\rm sc}$. Nevertheless, the Higuchi bound and the condition that the tower mass scale is higher than the gravitino mass provide the upper bound on $m_{\rm sc}$ determined by the lowest tower mass scale (or gravitino mass). This bound also can be interpreted as the lower bound on the lowest tower mass scale determined by $m_{\rm sc}$. We investigate this bound in detail when the throat containing $\overline{\rm D3}$-branes is strongly and weakly warped, respectively.
The theory of modular flow has proved extremely useful for applying thermodynamic reasoning to out-of-equilibrium states in quantum field theory. However, the standard proofs of the fundamental theorems of modular flow use machinery from Fourier analysis on Banach spaces, and as such are not especially transparent to an audience of physicists. In this article, I present a construction of modular flow that differs from existing treatments. The main pedagogical contribution is that I start with thermal physics via the KMS condition, and derive the modular operator as the only operator that could generate a thermal time-evolution map, rather than starting with the modular operator as the fundamental object of the theory. The main technical contribution is a new proof of the fundamental theorem stating that modular flow is a symmetry. The new proof circumvents the delicate issues of Fourier analysis that appear in previous treatments, but is still mathematically rigorous.
The solution of Bethe ansatz equations for XXZ spin chain with the parameter $q$ being a root of unity is infamously subtle. In this work, we develop the rational $Q$-system for this case, which offers a systematic way to find all physical solutions of the Bethe ansatz equations at root of unity. The construction contains two parts. In the first part, we impose additional constraints to the rational $Q$-system. These constraints eliminate the so-called Fabricius-McCoy (FM) string solutions, yielding all primitive solutions. In the second part, we give a simple procedure to construct the descendant tower of any given primitive state. The primitive solutions together with their descendant towers constitute the complete Hilbert space. We test our proposal by extensive numerical checks and apply it to compute the torus partition function of the 6-vertex model at root of unity.
In this note, we study $1/4$- and $1/2$-BPS co-dimension two superconformal defects in the $6d$ $\mathcal{N}=(2,0)$ $A_{N-1}$ SCFT at large $N$ using their holographic descriptions as solutions of $11d$ supergravity. In this regime, we are able to compute the defect contribution to the sphere entanglement entropy and the change in the stress-energy tensor one-point function due to the presence of the defect using holography. From these quantities, we are then able to unambiguously compute the values for two of the twenty-nine total Weyl anomaly coefficients that characterize $4d$ conformal defects in six and higher dimensions. We are able to demonstrate the consistency of the supergravity description of the defect theories with the average null energy condition on the field theory side. For each class of defects that we consider, we also show that the A-type Weyl anomaly coefficient is non-negative.
The contribution of elliptic fixed points to the scalar Casimir energy on compact quotients of the upper half hyperbolic plane is computed for a propagation operator conformal in three dimensions. The expression involves derivatives of two-dimensional Barnes zeta-functions which are reduced to Hurwitz zeta-functions for numerical purposes. The values are all positive for any elliptic order.
N=2 conformal supergravity in five dimensions is constructed via a systematic off-shell reduction scheme from maximal conformal supergravity in six dimensions which is (2,0). The dimensional reduction of the (2,0) Weyl multiplet in six dimensions gives us the Weyl multiplet in five dimensions which is a dilaton Weyl multiplet as it has a dilaton scalar. The dimensional reduction of the (2,0) tensor multiplet in six dimensions gives us the N=2 vector multiplet in five dimensions coupled to conformal supergravity. We also comment on Nahm's classification regarding the non-existence of an N=2 superconformal algebra in five dimensions and why it does not contradict the existence of N=2 conformal supergravity in five dimensions that is constructed in this paper.
Measurements of the substructure of top-quark jets are presented, using 140 fb$^{-1}$ of 13 TeV $pp$ collision data recorded with the ATLAS detector at the LHC. Top-quark jets reconstructed with the anti-$k_{t}$ algorithm with a radius parameter $R=1.0$ are selected in top-quark pair ($t\bar{t}$) events where one top quark decays semileptonically and the other hadronically, or where both top quarks decay hadronically. The top-quark jets are required to have transverse momentum $p_\mathrm{T} > 350$ GeV, yielding large samples of data events with jet $p_\mathrm{T}$ values between 350 and 600 GeV. One- and two-dimensional differential cross-sections for eight substructure variables, defined using only the charged components of the jets, are measured in a particle-level phase space by correcting for the smearing and acceptance effects induced by the detector. The differential cross-sections are compared with the predictions of several Monte Carlo simulations in which top-quark pair-production quantum chromodynamic matrix-element calculations at next-to-leading-order precision in the strong coupling constant $\alpha_\mathrm{S}$ are passed to leading-order parton shower and hadronization generators. The Monte Carlo predictions for measures of the broadness, and also the two-body structure, of the top-quark jets are found to be in good agreement with the measurements, while variables sensitive to the three-body structure of the top-quark jets exhibit some tension with the measured distributions.
Recent work has demonstrated that graph neural networks (GNNs) can match the performance of traditional algorithms for charged particle tracking while improving scalability to meet the computing challenges posed by the HL-LHC. Most GNN tracking algorithms are based on edge classification and identify tracks as connected components from an initial graph containing spurious connections. In this talk, we consider an alternative based on object condensation (OC), a multi-objective learning framework designed to cluster points (hits) belonging to an arbitrary number of objects (tracks) and regress the properties of each object. Building on our previous results, we present a streamlined model and show progress toward a one-shot OC tracking algorithm in a high-pileup environment.
The High-Luminosity LHC will deliver an unprecedented instantaneous luminosity, requiring all experiments to upgrade their detectors to sustain the higher background rates. The upgrade of the CMS Muon spectrometer includes three stations of triple-GEM detectors. We present the status of the commissioning and performance validation of the three GEM stations: GE1/1, which is taking data in Run 3, GE2/1, for which the first detectors will be installed in 2024, and ME0, which has undergone several performance studies for high-rate and longevity and will start its mass production in 2024.
We investigate the possibility to apply quantum machine learning techniques for data analysis, with particular regard to an interesting use-case in high-energy physics. We propose an anomaly detection algorithm based on a parametrized quantum circuit. This algorithm has been trained on a classical computer and tested with simulations as well as on real quantum hardware. Tests on NISQ devices have been performed with IBM quantum computers. For the execution on quantum hardware specific hardware driven adaptations have been devised and implemented. The quantum anomaly detection algorithm is able to detect simple anomalies like different characters in handwritten digits as well as more complex structures like anomalous patterns in the particle detectors produced by the decay products of long-lived particles produced at a collider experiment. For the high-energy physics application, performance is estimated in simulation only, as the quantum circuit is not simple enough to be executed on the available quantum hardware. This work demonstrates that it is possible to perform anomaly detection with quantum algorithms, however, as amplitude encoding of classical data is required for the task, due to the noise level in the available quantum hardware, current implementation cannot outperform classic anomaly detection algorithms based on deep neural networks.
Measurements of both the inclusive and differential production cross sections of a top-quark-top-antiquark pair in association with a $Z$ boson ($t\bar{t}Z$) are presented. Final states with two, three or four isolated leptons (electrons or muons) are targeted. The measurements use the data recorded by the ATLAS detector in $pp$ collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider during the years 2015-2018, corresponding to an integrated luminosity of $140$ fb$^{-1}$. The inclusive cross section is measured to be $\sigma_{t\bar{t}Z}= 0.86 \pm 0.04~\mathrm{(stat.)} \pm 0.04~\mathrm{(syst.)}~$pb and found to be in agreement with the most advanced Standard Model predictions. The differential measurements are presented as a function of a number of observables that probe the kinematics of the $t\bar{t}Z$ system. Both the absolute and normalised differential cross-section measurements are performed at particle level and parton level for specific fiducial volumes, and are compared with NLO+NNLL theoretical predictions. The results are interpreted in the framework of Standard Model effective field theory and used to set limits on a large number of dimension-6 operators involving the top quark. The first measurement of spin correlations in $t\bar{t}Z$ events is presented: the results are in agreement with the Standard Model expectations, and the null hypothesis of no spin correlations is disfavoured with a significance of $1.8$ standard deviations.
The standard model (SM) of particle physics represents a theoretical paradigm for the description of the fundamental forces of nature. Despite its broad applicability, the SM does not enable the description of all physically possible events. The detection of events that cannot be described by the SM, which are typically referred to as anomalous, and the related potential discovery of exotic physical phenomena is a non-trivial task. The challenge becomes even greater with next-generation colliders that will produce even more events with additional levels of complexity. The additional data complexity motivates the search for unsupervised anomaly detection methods that do not require prior knowledge about the underlying models. In this work, we develop such a technique. More explicitly, we employ a quantum generative adversarial network to identify anomalous events. The method learns the background distribution from SM data and, then, determines whether a given event is characteristic for the learned background distribution. The proposed quantum-powered anomaly detection strategy is tested on proof-of-principle examples using numerical simulations and IBM Quantum processors. We find that the quantum generative techniques using ten times fewer training data samples can yield comparable accuracy to the classical counterpart for the detection of the Graviton and Higgs particles. Additionally, we empirically compute the capacity of the quantum model and observe an improved expressivity compared to its classical counterpart.
In the realm of dijet searches in high-energy physics, a perplexing challenge has emerged: with experiments producing more and more data, our traditional ways of describing the dijet mass spectrum using analytic functions are struggling to keep up. To address this, we suggest the application of the anomaly detection approach to eliminate less interesting background events based on event final states. This method not only bypasses the limitations of conventional background models but also significantly enhances our ability to detect potential signals of new physics. Through simulations that mimic the conditions of the upcoming High-Luminosity Large Hadron Collider, we demonstrate the strength and efficiency of this approach in dealing with large data volumes. The integration of unsupervised machine learning into our experimental framework paves the way for a promising avenue to unveil hidden physics discoveries within the overwhelming influx of data.
The longitudinal and transverse spin transfers to $\Lambda$ ($\overline{\Lambda}$) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti-)strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, $D_{LL}$, and the transverse spin transfer coefficient, $D_{TT}$, to $\Lambda$ and $\overline{\Lambda}$ in polarized proton-proton collisions at $\sqrt{s}$ = 200 GeV by the STAR experiment at RHIC. The data set includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb$^{-1}$, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both data sets have about twice the statistics of previous results and cover a kinematic range of $|\eta_{\Lambda(\overline{\Lambda})}|$ $<$ 1.2 and transverse momentum $p_{T,{\Lambda(\overline{\Lambda})}}$ up to 8 GeV/$c$. We also report the first measurements of the hyperon spin transfer coefficients $D_{LL}$ and $D_{TT}$ as a function of the fractional jet momentum $z$ carried by the hyperon, which can provide more direct constraints on the polarized fragmentation functions.
The field of superconducting quantum computing, based on Josephson junctions, has recently seen remarkable strides in scaling the number of logical qubits. In particular, the fidelities of one- and two-qubit gates are close to the breakeven point with the novel error mitigation and correction methods. Parallel to these advances is the effort to expand the Hilbert space within a single device by employing high-dimensional qubits, otherwise known as qudits. Research has demonstrated the possibility of driving higher-order transitions in a transmon or designing innovative multimode superconducting circuits, termed multimons. These advances can significantly expand the computational basis while simplifying the interconnects in a large-scale quantum processor. This thesis provides a detailed introduction to the superconducting qudit and demonstrates a comprehensive analysis of decoherence in an artificial atom with more than two levels using Lindblad master equations and stochastic master equations (SMEs). After extending the theory of the design, control, and readout of a conventional superconducting qubit to that of a qudit, the thesis focuses on modeling the dispersive measurement of a transmon qutrit in an open quantum system using quadrature detections. Under the Markov assumption, master equations with different levels of abstraction are proposed and solved; in addition, both the ensemble-averaged and the quantum-jump approach of decoherence analysis are presented and compared analytically and numerically. The thesis ends with a series of experimental results on a transmon-type qutrit, verifying the validity of the stochastic model.
Studies on Quantum Computing have been developed since the 1980s, motivating researches on quantum algorithms better than any classical algorithm possible. An example of such algorithms is Grover's algorithm, capable of finding $k$ (marked) elements in an unordered database with $N$ elements using $O(\sqrt{N/k})$ steps. Grover's algorithm can be interpreted as a quantum walk in a complete graph (with loops) containing $N$ vertices from which $k$ are marked. This interpretation motivated search algorithms in other graphs -- complete bipartite graph, grid, and hypercube. Using Grover's algorithm's linear operator, the quantum counting algorithm estimates the value of $k$ with an error of $O(\sqrt{k})$ using $O(\sqrt{N})$ steps. This work tackles the problem of using the quantum counting algorithm for estimating the value $k$ of marked elements in other graphs; more specifically, the complete bipartite graph. It is concluded that for a particular case, running the proposed algorithm at most $t$ times wields an estimation of $k$ with an error of $O(\sqrt{k})$ using $O(t\sqrt{N})$ steps and success probability of at least $(1 - 2^{-t})8/\pi^2$.
A variational expression of the reduced relative entropy is given. A reduced Tsallis relative entropy is defined and some results are given. In particular, the convexity of the reduced Tsallis relative entropy is given. An interpolational inequality between Golden--Thompson and Jensen's trace inequalitie is given for one--parameter extended exponential function and positive definite matrices. In addition, a lower bound of the reduced Tsallis relative entropy is given under a certain assumption, by showing a variational expression of the reduced Tsallis relative entropy. Finally, an upper bound of the reduced Tsallis relative entropy is given.
The rapid advancements in quantum computing as ushered in a new era for computer simulations, presenting groundbreaking opportunities across diverse disciplines. Central to this revolution is the quantum processor's capacity to entangle qubits, unlocking unprecedented possibilities for addressing computational challenges on an extreme scale, far beyond the reach of classical computing. In this study, we explore how quantum computing can be employed to enhance computational mechanics. Our focus is on the analysis of Representative Volume Element (RVE) within the framework of multiscale solid mechanics. We introduce an innovative quantum algorithm designed to solve the RVE problem. This algorithm is capable of compute RVEs of discretization size $N$ in $\mathcal{O}(\textrm{Poly log}(N))$ time, thus achieving an exponential speed-up over traditional classical computing approaches that typically scales linearly with $N$. We validate our approach with case studies including the solution of one and two dimensional Poisson's equation, as well as an RVE of a composite bar with piece-wise constant phases. We provide quantum circuit designs that requires only $\mathcal{O}(\textrm{Poly log}(N))$ universal quantum gates,underscoring the efficiency of our approach. Our work suggests a major way in which quantum computing can be combined with and brought to bear on computational mechanics.
Exploring operational regimes of many-body cavity QED with multi-level atoms remains an exciting research frontier for their enhanced storage capabilities of intra-level quantum correlations. In this work, we propose an extension of a prototypical many-body cavity QED experiment from a two to a four-level description by optically addressing a combination of momentum and spin states of the ultracold atoms in the cavity. The resulting model comprises a pair of Dicke Hamiltonians constructed from pseudo-spin operators, effectively capturing two intertwined superradiant phase transitions. The phase diagram reveals regions featuring weak and strong entangled states of spin and momentum atomic degrees of freedom. These states exhibit different dynamical responses, ranging from slow to fast relaxation, with the added option of persistent entanglement temporal oscillations. We discuss the role of cavity losses in steering the system dynamics into such entangled states and propose a readout scheme that leverages different light polarizations within the cavity. Our work paves the way to connect the rich variety of non-equilibrium phase transitions that occur in many-body cavity QED to the buildup of quantum correlations in systems with multi-level atom descriptions.
Solving optimization problems is a key task for which quantum computers could possibly provide a speedup over the best known classical algorithms. Particular classes of optimization problems including semi-definite programming (SDP) and linear programming (LP) have wide applicability in many domains of computer science, engineering, mathematics, and physics. Here we focus on semi-definite and linear programs for which the dimensions of the variables involved are exponentially large, so that standard classical SDP and LP solvers are not helpful for such large-scale problems. We propose the QSlack and CSlack methods for estimating their optimal values, respectively, which work by 1) introducing slack variables to transform inequality constraints to equality constraints, 2) transforming a constrained optimization to an unconstrained one via the penalty method, and 3) replacing the optimizations over all possible non-negative variables by optimizations over parameterized quantum states and parameterized probability distributions. Under the assumption that the SDP and LP inputs are efficiently measurable observables, it follows that all terms in the resulting objective functions are efficiently estimable by either a quantum computer in the SDP case or a quantum or probabilistic computer in the LP case. Furthermore, by making use of SDP and LP duality theory, we prove that these methods provide a theoretical guarantee that, if one could find global optima of the objective functions, then the resulting values sandwich the true optimal values from both above and below. Finally, we showcase the QSlack and CSlack methods on a variety of example optimization problems and discuss details of our implementation, as well as the resulting performance. We find that our implementations of both the primal and dual for these problems approach the ground truth, typically achieving errors of order $10^{-2}$.
The Tavis-Cummings model is a paradigmatic central-mode model where a set of two-level quantum emitters (spins) are coupled to a collective cavity mode. Here we study the eigenstate spectrum, its localization properties and the effect on dynamics, focusing on the two-excitation sector relevant for nonlinear photonics. These models admit two sources of disorder: in the coupling between the spins and the cavity and in the energy shifts of the individual spins. While this model was known to be exactly solvable in the limit of a homogeneous coupling and inhomogeneous energy shifts, we here establish the solvability in the opposite limit of a homogeneous energy shift and inhomogeneous coupling, presenting the exact solution and corresponding conserved quantities. We identify three different classes of eigenstates, exhibiting different degrees of multifractality and semilocalization closely tied to the integrable points, and study their stability to perturbations away from these solvable points. The dynamics of the cavity occupation number away from equilibrium, exhibiting boson bunching and a two-photon blockade, is explicitly related to the localization properties of the eigenstates and illustrates how these models support a collective spin description despite the presence of disorder.
The Hayden-Preskill protocol probes the capability of information recovery from local subsystems after unitary dynamics. As such it resolves the capability of quantum many-body systems to dynamically implement a quantum error-correcting code. The transition to coding behavior has been mostly discussed using effective approaches, such as entanglement membrane theory. Here, we present exact results on the use of Hayden-Preskill recovery as a dynamical probe of scrambling in local quantum many-body systems. We investigate certain classes of unitary circuit models, both structured Floquet (dual-unitary) and Haar-random circuits. We discuss different dynamical signatures corresponding to information transport or scrambling, respectively, that go beyond effective approaches. Surprisingly, certain chaotic circuits transport information with perfect fidelity. In integrable dual-unitary circuits, we relate the information transmission to the propagation and scattering of quasiparticles. Using numerical and analytical insights, we argue that the qualitative features of information recovery extend away from these solvable points. Our results suggest that information recovery protocols can serve to distinguish chaotic and integrable behavior, and that they are sensitive to characteristic dynamical features, such as long-lived quasiparticles or dual-unitarity.
There are two major approaches to building good machine learning algorithms: feeding lots of data into large models, or picking a model class with an ''inductive bias'' that suits the structure of the data. When taking the second approach as a starting point to design quantum algorithms for machine learning, it is important to understand how mathematical structures in quantum mechanics can lead to useful inductive biases in quantum models. In this work, we bring a collection of theoretical evidence from the Quantum Cognition literature to the field of Quantum Machine Learning to investigate how non-commutativity of quantum observables can help to learn data with ''order effects'', such as the changes in human answering patterns when swapping the order of questions in a survey. We design a multi-task learning setting in which a generative quantum model consisting of sequential learnable measurements can be adapted to a given task -- or question order -- by changing the order of observables, and we provide artificial datasets inspired by human psychology to carry out our investigation. Our first experimental simulations show that in some cases the quantum model learns more non-commutativity as the amount of order effect present in the data is increased, and that the quantum model can learn to generate better samples for unseen question orders when trained on others - both signs that the model architecture suits the task.
The emission linewidth in active medium emerges due to homogeneous and inhomogeneous broadening. We demonstrate that in lasers with inhomogeneous broadening there is a critical pump rate, above which the special mode forms. This mode consists of locked-in oscillations of cavity mode and of the active particles with different transition frequencies. Below the critical value of the pump rate, the radiation spectrum of the laser has a Gaussian profile, provided that inhomogeneous broadening is dominant. Above the critical value of pump rate, the special mode mostly determines the laser radiation spectrum. As the result, the spectrum attains Lorentz shape characteristic for homogeneous broadening. We demonstrate that the formation of the special mode precedes lasing and that the critical pump rate plays the role of lasing prethreshold. We obtain expressions for the threshold and generation frequency of single-mode laser where both homogeneous and inhomogeneous broadening are present.
We introduce a family of identities that express general linear non-unitary evolution operators as a linear combination of unitary evolution operators, each solving a Hamiltonian simulation problem. This formulation can exponentially enhance the accuracy of the recently introduced linear combination of Hamiltonian simulation (LCHS) method [An, Liu, and Lin, Physical Review Letters, 2023]. For the first time, this approach enables quantum algorithms to solve linear differential equations with both optimal state preparation cost and near-optimal scaling in matrix queries on all parameters.
Measurement-based quantum computation relies on single qubit measurements of large multipartite entangled states, so-called lattice-graph or cluster states. Graph states are also an important resource for quantum communication, where tree cluster states are a key resource for one-way quantum repeaters. A photonic realization of this kind of state would inherit many of the benefits of photonic platforms, such as very little dephasing due to weak environmental interactions and the well-developed infrastructure to route and measure photonic qubits. In this work, a linear cluster state and GHZ state generation scheme is developed for group-IV color centers. In particular, this article focuses on an in-depth investigation of the required control operations, including the coherent spin and excitation gates. We choose an off-resonant Raman scheme for the spin gates, which can be much faster than microwave control. We do not rely on a reduced level scheme and use efficient approximations to design high-fidelity Raman gates. We benchmark the spin-control and excitation scheme using the tin vacancy color center coupled to a cavity, assuming a realistic experimental setting. Additionally, the article investigates the fidelities of the Raman and excitation gates in the presence of radiative and non-radiative decay mechanisms. Finally, a quality measure is devised, which emphasizes the importance of fast and high-fidelity spin gates in the creation of large entangled photonic states.
Suppressing errors is the central challenge for useful quantum computing, requiring quantum error correction for large-scale processing. However, the overhead in the realization of error-corrected ``logical'' qubits, where information is encoded across many physical qubits for redundancy, poses significant challenges to large-scale logical quantum computing. Here we report the realization of a programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits. Utilizing logical-level control and a zoned architecture in reconfigurable neutral atom arrays, our system combines high two-qubit gate fidelities, arbitrary connectivity, as well as fully programmable single-qubit rotations and mid-circuit readout. Operating this logical processor with various types of encodings, we demonstrate improvement of a two-qubit logic gate by scaling surface code distance from d=3 to d=7, preparation of color code qubits with break-even fidelities, fault-tolerant creation of logical GHZ states and feedforward entanglement teleportation, as well as operation of 40 color code qubits. Finally, using three-dimensional [[8,3,2]] code blocks, we realize computationally complex sampling circuits with up to 48 logical qubits entangled with hypercube connectivity with 228 logical two-qubit gates and 48 logical CCZ gates. We find that this logical encoding substantially improves algorithmic performance with error detection, outperforming physical qubit fidelities at both cross-entropy benchmarking and quantum simulations of fast scrambling. These results herald the advent of early error-corrected quantum computation and chart a path toward large-scale logical processors.
Correlation between transmon and its composite Josephson junctions (JJ) plays an important role in designing new types of superconducting qubits based on quantum materials. It is desirable to have a type of device that not only allows exploration for use in quantum information processing but also probing intrinsic properties in the composite JJs. Here, we construct a flux-tunable 3D transmon-type superconducting quantum circuit made of graphene as a proof-of-concept prototype device. This 3D transmon-type device not only enables coupling to 3D cavities for microwave probes but also permits DC transport measurements on the same device, providing useful connections between transmon properties and critical currents associated with JJ's properties. We have demonstrated how flux-modulation in cavity frequency and DC critical current can be correlated under the influence of Fraunhofer pattern of JJs in an asymmetric SQUID. The correlation analysis was further extended to link the flux-modulated transmon properties, such as flux-tunability in qubit and cavity frequencies, with SQUID symmetry analysis based on DC measurements. Our study paves the way towards integrating novel materials for exploration of new types of quantum devices for future technology while probing underlying physics in the composite materials.
High-dimensional teleportation provides various benefits in quantum networks and repeaters, but all these advantages rely on the high-quality distribution of high-dimensional entanglement over a noisy channel. It is essential to consider correlation effects when two entangled qutrits travel consecutively through the same channel. In this paper, we present two strategies for enhancing qutrit teleportation in correlated amplitude damping (CAD) noise by weak measurement (WM) and environment-assisted measurement (EAM). The fidelity of both approaches has been dramatically improved due to the probabilistic nature of WM and EAM. We have observed that the correlation effects of CAD noise result in an increase in the probability of success. A comparison has demonstrated that the EAM scheme consistently outperforms the WM scheme in regard to fidelity. Our research expands the capabilities of WM and EAM as quantum techniques to combat CAD noise in qutrit teleportation, facilitating the development of advanced quantum technologies in high-dimensional systems.
We study the effect of PT-symmetric non-hermiticity on the transport of edge state probability density arising as a result of a quench. A hybrid system involving a PT-symmetric SSH region sandwiched between two plain SSH systems is designed to study the dynamics. Geometrical arguments and numerical calculations were made to ascertain the nature of edge states. We then compute the quench dynamics numerically and demonstrate that the post-quench probability density light cones exhibit contrasting shapes as a result of asymmetrical reflections from the non-Hermitian part of the system depending on the direction of propagation of the transporting wave and, hence, on the initial localization of the edge state.
Quantum state discrimination is a central task in many quantum computing settings where one wishes to identify what quantum state they are holding. We introduce a framework that generalizes many of its variants and present a hybrid quantum-classical algorithm based on semidefinite programming to calculate the maximum reward when the states are pure and have efficient circuits. To this end, we study the (not necessarily linearly independent) pure state case and reduce the standard SDP problem size from $2^n L$ to $N L$ where $n$ is the number of qubits, $N$ is the number of states, and $L$ is the number of possible guesses (typically $L = N$). As an application, we give now-possible algorithms for the quantum change point identification problem which asks, given a sequence of quantum states, determine the time steps when the quantum states changed. With our reductions, we are able to solve SDPs for problem sizes of up to $220$ qubits in about $8$ hours and we also give heuristics which speed up the computations.
We study the spectrum of the Dirac Hamiltonian in one space dimension for a single electron in the electrostatic potential of a point nucleus, in the Born-Oppenheimer approximation where the nucleus is assumed fixed at the origin. The potential is screened at large distances so that it goes to zero exponentially at spatial infinity. We show that the Hamiltonian is essentially self-adjoint, the essential spectrum has the usual gap $(-mc^2,mc^2)$ in it, and that there are only finitely many eigenvalues in that gap, corresponding to ground and excited states for the system. We find a one-to-one correspondence between the eigenfunctions of this Hamiltonian and the heteroclinic saddle-saddle connectors of a certain dynamical system on a finite cylinder. We use this correspondence to study how the number of bound states changes with the nuclear charge.
We analyse two party non-local games whose predicate requires Alice and Bob to generate matching bits, and their three party extensions where a third player receives all inputs and is required to output a bit that matches that of the original players. We propose a general device independent quantum key distribution protocol for the subset of such non-local games that satisfy a monogamy-of-entanglement property characterised by a gap in the maximum winning probability between the bipartite and tripartite versions of the game. This gap is due to the optimal strategy for two players requiring entanglement, which due to its monogamy property cannot be shared with any additional players. Based solely on the monogamy-of-entanglement property, we provide a simple proof of information theoretic security of our protocol. Lastly, we numerically optimize the finite and asymptotic secret key rates of our protocol using the magic square game as an example, for which we provide a numerical bound on the maximal tripartite quantum winning probability which closely matches the bipartite classical winning probability. Further, we show that our protocol is robust for depolarizing noise up to about $2.2\%$, providing the first such bound for general attacks for magic square based quantum key distribution.
We present a theoretical study of resonance lifetimes in a two-component three-body system, specifically examining the decay of three-body resonances into a deep dimer and an unbound particle. Utilising the Gaussian expansion method together with the complex scaling method, we obtain the widths of these resonances from first principles. We focus on mass ratios in the typical range for mixtures of ultracold atoms and reveal a pronounced dependence of the resonance widths on the mass ratio: a distinct maximum near the equal-mass scenario and a rapid decrease away from it. Moreover, we show that this behaviour is not covered by the analytical formula of Pen'kov~[Phys. Rev. A 60, 3756 (1999)]. Notably, near the mass ratio for Caesium-Lithium mixtures, we obtain nearly vanishing widths of the resonances which validates to treat them in the bound state approximation. In addition, we perform our analysis on the resonance widths in both one and three dimensions and find that their qualitative dependence on the mass ratio agrees.
Predicting the properties of strongly correlated materials is a significant challenge in condensed matter theory. The widely used dynamical mean-field theory faces difficulty in solving quantum impurity models numerically. Hybrid quantum--classical algorithms such as variational quantum eigensolver emerge as a potential solution for quantum impurity models. A common challenge in these algorithms is the rapid growth of the number of variational parameters with the number of spin-orbitals in the impurity. In our approach to this problem, we develop compact ansatzes using a combination of two different strategies. First, we employ compact physics-inspired ansatz, $k$-unitary cluster Jastrow ansatz, developed in the field of quantum chemistry. Second, we eliminate largely redundant variational parameters of physics-inspired ansatzes associated with bath sites based on physical intuition. This is based on the fact that a quantum impurity model with a star-like geometry has no direct hopping between bath sites. We benchmark the accuracy of these ansatzes for both ground-state energy and dynamic quantities by solving typical quantum impurity models with/without shot noise. The results suggest that we can maintain the accuracy of ground-state energy while we drop the number of variational parameters associated with bath sites. Furthermore, we demonstrate that a moment expansion, when combined with the proposed ansatzes, can calculate the imaginary-time Green's functions under the influence of shot noise. This study demonstrates the potential for addressing complex impurity models in large-scale quantum simulations with fewer variational parameters without sacrificing accuracy.
Quantum key distribution (QKD) protocols are essential to guarantee information-theoretic security in quantum communication. Although there was some previous work on quantum group key distribution, they still face many challenges under a ``\textit{dynamic}'' group communication scenario. In particular, when the group keys need to be updated in real-time for each user joining or leaving to ensure secure communication properties, i.e., forward confidentiality and backward confidentiality. However, current protocols require a large amount of quantum resources to update the group keys, and this makes them impractical for handling large and dynamic communication groups. In this paper, we apply the notion of ``{\em tree key graph}'' to the quantum key agreement and propose two dynamic Quantum Group Key Agreement (QGKA) protocols for a join or leave request in group communications. In addition, we analyze the quantum resource consumption of our proposed protocols. The number of qubits required per join or leave only increases logarithmically with the group size. As a result, our proposed protocols are more practical and scalable for large and dynamic quantum group communications.
For a wide range of applications a fast, non-destructive, remote, and sensitive identification of samples with predefined characteristics is preferred instead of their full characterization. Here, we report on the experimental implementation of a nonlocal quantum measurement scheme enabling to distinguish different transparent and birefringent samples by means of polarization-entangled photon pairs and remote state preparation. On an example set of more than 80 objects with varying Mueller matrices we show that only two coincidence measurements are already sufficient for successful discrimination in contrast to at least 8 required for a comprehensive inspection. The decreased number of measurements and the sample set significantly exceeding a typical set size for various problems demonstrate the high potential of the method for applications aiming at biomedical diagnostics, remote sensing, and other classification/detection tasks.
We show that the performance of critical quantum metrology protocols, counter-intuitively, can be enhanced by finite temperature. We consider a toy-model squeezing Hamiltonian, the Lipkin-Meshkov-Glick model and the paradigmatic Ising model. We show that the temperature enhancement of the quantum Fisher information can be achieved by adiabatic preparation of the critical state and by preparing it directly in the proximity of the critical point. We also find a relatively simple, however, non-optimal measurement capable of harnessing finite temperature to increase the parameter estimation sensitivity. Therefore, we argue that temperature can be considered as a resource in critical quantum metrology.
The Electron Multiplying Charge Coupled Devices (EMCCD), owing to their high quantum efficiency and decent spatial resolution, are widely used to study typical quantum optical phenomena such as spatial entanglement and related applications. Researchers have already developed a procedure that enables us to statistically determine whether a pixel detects a single photon or not based on whether its output is higher or lower than the estimated noise level. However, these techniques are limited to extremely low photon numbers ( $\approx 0.15$ mean number of photons per pixel per exposure), allowing for at most one photon per pixel. This limitation hinders applications due to the large number of frames required for any study. In this work, we present a method to estimate the mean rate of photons per pixel per frame for a specific exposure time. Subsequently, we make a statistical estimate of the number of photons ($\geq 1$) incident on each pixel. This allows us to effectively utilize the EMCCD as a photon number resolving device, which significantly reduces the required experimentation time. As evidence of our approach, we quantify contrast in quantum correlation exhibited by a pair of spatially entangled photons generated by Spontaneous Parametric Down Conversion process. We employ the standard methods commonly used within the scientific community for comparison with our proposed method. We find an enhancement in the signal to noise ratio by about a factor of 3 for identical number of frames. This implies that this technique can achieve excellent results only within half the data collection time as compared to the conventional techniques.
In the quest for fault-tolerant quantum computation using superconducting processors, accurate performance assessment and continuous design optimization stands at the forefront. To facilitate both meticulous simulation and streamlined design optimization, we introduce a multi-level simulation framework that spans both Hamiltonian and quantum error correction levels, and is equipped with the capability to compute gradients efficiently. This toolset aids in design optimization, tailored to specific objectives like quantum memory performance. Within our framework, we investigate the often-neglected spatially correlated unitary errors, highlighting their significant impact on logical error rates. We exemplify our approach through the multi-path coupling scheme of fluxonium qubits.
Integration of Quantum Key Distribution (QKD) in existing telecommunication infrastructure is crucial for the widespread adoption of this quantum technology, which offers the distillation of unconditionally secure keys between users. In this letter, we report a field trial between the Points of Presence (POPs) placed in Treviso and in Venezia - Mestre, Italy, exploiting the QuKy commercial polarization-based QKD platforms developed by ThinkQuantum srl and two different standards of single-mode optical fibers, i.e. G.652 and G.655, as a quantum channel. In this field trial, several configurations were tested, including the co-existence of classical and quantum signals over the same fiber, providing a direct comparison between the performances of the G.652 and G.655 fiber standards for QKD applications.
Quantum technologies rely heavily on accurate control and reliable readout of quantum systems. Current experiments are limited by numerous sources of noise that can only be partially captured by simple analytical models and additional characterization of the noise sources is required. We test the ability of readout error mitigation to correct realistic noise found in systems composed of quantum two-level objects (qubits). To probe the limit of such methods, we designed a universal readout error mitigation protocol based on quantum state tomography (QST), which estimates the density matrix of a quantum system, and quantum detector tomography (QDT), which characterizes the measurement procedure. By treating readout error mitigation in the context of state tomography the method becomes largely device-, architecture-, noise source-, and quantum state-independent. We implement this method on a superconducting qubit and benchmark the increase in reconstruction fidelity for QST. We characterize the performance of the method by varying important noise sources, such as suboptimal readout signal amplification, insufficient resonator photon population, off-resonant qubit drive, and effectively shortened $T_1$ and $T_2$ decay times. As a result, we identified noise sources for which readout error mitigation worked well, and observed decreases in readout infidelity by a factor of up to 30.
The relativistic quantum equation is proposed for the complex wave function, which has the meaning of a probability amplitude. The Lagrangian formulation of the proposed theory is developed. The problem of spreading of a wave packet in an unlimited space is solved. The relativistic correction to the energy levels of a harmonic oscillator is found, leading to a violation of their equidistance.
The rate and security of quantum communications between users placed at arbitrary points of a quantum communication network depend on the structure of the network, on its extension and on the nature of the communication channels. In this work we propose a strategy of network optimization that intertwines classical network approaches and quantum information theory. Specifically, by suitably defining a quantum efficiency functional, we identify the optimal quantum communication connections through the network by balancing security and the quantum communication rate. The optimized network is then constructed as the network of the maximal quantum efficiency connections and its performance is evaluated by studying the scaling of average properties as functions of the number of nodes and of the network spatial extension.
We show that counting the number of collisions (re-sampled bitstrings) when measuring a random quantum circuit provides a practical benchmark for the quality of a quantum computer and a quantitative noise characterization method. We analytically estimate the difference in the expected number of collisions when sampling bitstrings from a pure random state and when sampling from the classical uniform distribution. We show that this quantity, if properly normalized, can be used as a "collision anomaly" benchmark or as a "collision volume" test which is similar to the well-known quantum volume test, with advantages (no classical computing cost) and disadvantages (high sampling cost). We also propose to count the number of cross-collisions between two independent quantum computers running the same random circuit in order to obtain a cross-validation test of the two devices. Finally, we quantify the sampling cost of quantum collision experiments. We find that the sampling cost for running a collision volume test on state-of-the-art processors (e.g.~20 effective clean qubits) is quite small: less than $10^5$ shots. For large-scale experiments in the quantum supremacy regime the required number of shots for observing a quantum signal in the observed number of collisions is currently infeasible ($>10^{12}$), but not completely out of reach for near-future technology.
We conducted a thorough evaluation of various state-of-the-art strategies to prepare the ground state wavefunction of a system on a quantum computer, specifically within the framework of variational quantum eigensolver (VQE). Despite the advantages of VQE and its variants, the current quantum computational chemistry calculations often provide inaccurate results for larger molecules, mainly due to the polynomial growth in the depth of quantum circuits and the number of two-qubit gates, such as CNOT gates. To alleviate this problem, we aim to design efficient quantum circuits that would outperform the existing ones on the current noisy quantum devices. In this study, we designed a novel quantum circuit that reduces the required circuit depth and number of two-qubit entangling gates by about 60%, while retaining the accuracy of the ground state energies close to the chemical accuracy. Moreover, even in the presence of device noise, these novel shallower circuits yielded substantially low error rates than the existing approaches for predicting the ground state energies of molecules. By considering the umbrella inversion process in ammonia molecule as an example, we demonstrated the advantages of this new approach and estimated the energy barrier for the inversion process.
Quantum Teleportation is a very useful scheme for transferring quantum information. Given that the quantum information is encoded in a state of a system of distinguishable particles, and given that the shared bi-partite entangled state is also that of a system of distinguishable particles, the optimal teleportation fidelity of the shared state is known to be $(F_{max}d+1)/(d+1)$ with $F_{max}$ being the `maximal singlet fraction' of the shared state. In the present work, we address the question of optimal teleportation fidelity given that the quantum information to be teleported is encoded in Fermionic modes while a $2N$-mode state of a system of Fermions (with maximum $2N$ no. of Fermions -- in the second quantization language) is shared between the sender and receiver with each party possessing $N$ modes of the $2N$-mode state. Parity Superselection Rule (PSSR) in Fermionic Quantum Theory (FQT) puts constraint on the allowed set of physical states and operations, and thereby, leads to a different notion of Quantum Teleportation. Due to PSSR, we introduce restricted Clifford twirl operations that constitute the Unitary 2-design in case of FQT, and show that the structure of the canonical form of Fermionic invariant shared state differs from that of the isotropic state -- the corresponding canonical invariant form for teleportation in Standard Quantum Theory (SQT). We provide a lower bound on the optimal teleportation fidelity in FQT and compare the result with teleportation in SQT. Surprisingly, we find that, under separable measurements on a bipartite Fermionic state, input and output states of the Fermionic teleportation channel cannot be distinguished operationally, even if a particular kind of resource state with `maximal singlet fraction' being less than unity is used.
Quantum Darwinism (QD) proposes that classical objectivity emerges from the broadcast of information about a microscopic degree of freedom into multiple fractions of a many-body environment. Such a broadcast of information is in sharp contrast with its scrambling under strong interaction. It was recently shown that quantum dynamics interpolating between broadcasting and scrambling may display sharp phase transitions of information propagation, named QD-encoding transitions. Here, we initiate their systematic study in generic, non-Clifford settings. First, in a general theoretical setup where the information propagation is modeled as an isometry, whose input qudit is entangled with a reference, we propose a probe of the transitions -- the distribution of the density matrix of the reference after measuring an environment fraction. This probe measures the classical correlation between the fraction and the injected information. We then apply the framework to two similar models defined by a tensor network on an expanding tree, modeling a noisy apparatus that attempts to broadcast the $z$ component of a spin-half. We derive an exact recursion relation of the density matrix distribution, which we analyze analytically and numerically. As a result we find three phases: QD, intermediate and encoding, and two continuous transitions. The encoding-intermediate transition describes the establishment of nonzero correlation between the reference and a small environment fraction, and can be probed by a ``coarse-grained'' measure of the total spin-$z$ of the fraction, which becomes non-Gaussian and symmetry breaking in the intermediate space. The QD-intermediate transition is about whether the correlation is perfect. It must be probed by fined-grained measures, and corresponds to a more subtle symmetry breaking in the replica space.
Ising machines are purported to be better at solving large-scale combinatorial optimisation problems better than conventional von Neumann computers. However, these Ising machines are widely believed to be heuristics, whose promise is observed empirically rather than obtained theoretically. We bridge this gap by considering an opto-electronic oscillator based coherent Ising machine, and providing the first analytical proof that under reasonable assumptions, the OEO-CIM is not a heuristic approach. We find and prove bounds on its performance in terms of the expected difference between the objective value at the final iteration and the optimal one, and on the number of iterations required by it. In the process, we emphasise on some of its limitations such as the inability to handle asymmetric coupling between spins, and the absence of external magnetic field applied on them (both of which are necessary in many optimisation problems), along with some issues in its convergence. We overcome these limitations by proposing suitable adjustments and prove that the improved architecture is guaranteed to converge to the optimum of the relaxed objective function.
The quantum dynamics of vibrational polaritonic states arising from the interaction of a bistable molecule with the quantized mode of a Fabry-Perot microcavity is investigated using an asymmetric double-well potential as a simplified one-dimensional model of a reactive molecule. After discussing the role of the light-matter coupling strength in the emergence of avoided crossings between polaritonic states, we investigate the possibility of using these crossings in order to trigger a dynamical switching of these states from one potential well to the other. Two schemes are proposed to achieve this coherent state switching, either by preparing the molecule in an appropriate vibrational excited state before inserting it into the cavity, or by applying a short laser pulse inside the cavity to obtain a coherent superposition of polaritonic states. The respective influences of the dipole amplitude and potential asymmetry on the coherent switching process are also discussed.
Steering is a type of quantum nonlocality that exhibits an inherent asymmetry between two observers. In a nondegenerate three-level laser coupled to a two-mode squeezed vacuum reservoir, we examine, under realistic experimental conditions, the Gaussian steering of two laser modes, $\mathcal{A}$ and $\mathcal{B}$, generated within the cascade transitions, respectively. We find that the $\mathcal{A}\rightarrow \mathcal{B}$ steerability is always higher than that from $\mathcal{B}\rightarrow \mathcal{A}$; in addition, the steering asymmetry cannot exceed $\ln 2$, which implies that the state $\hat{\varrho}_{\mathcal{AB}}$ never diverges to an extremal asymmetry state. We show how squeezed noise can play a constructive role in realizing one-way steering. As the main result, we demonstrate that the state $\hat{\varrho}_{\mathcal{AB}}$ can exhibit one-way steering solely from $\mathcal{A}\rightarrow \mathcal{B}$, which we show to emerge as a consequence of the fact that the intensity difference of the modes $\mathcal{A}$ and $\mathcal{B}$ is verified to remain always positive, irrespective of the physical and environmental parameters of $\hat{\varrho}_{\mathcal{AB}}$. The generated unidirectional one-way steering may provide a useful resource for the distribution of the trust in future asymmetric quantum information tasks.
We describe a protocol for the universal control of non-ideal $\pi$-periodic superconducting qubits. Our proposal relies on a $\pi$-SQUID: a superconducting loop formed by two $\pi$-periodic circuit elements, with an external magnetic flux threading the circuit. The system exhibits an extensive sweet spot around half-flux where residual $2\pi$-periodic Cooper pair tunneling is highly suppressed. We demonstrate that universal single-qubit operations can be realised by tuning the flux adiabatically and diabatically within this broad sweet spot. We also assess how residual $2\pi$-periodicity in $\pi$-SQUIDs impacts holonomic phase gates.
Our proposal introduces a customization of the rodeo algorithm that enables us to determine the number of states associated with all energy levels of a quantum system without explicitly solving the Schr\"odinger equation. Quantum computers, with their innate ability to address the intricacies of quantum systems, make this approach particularly promising for the study of the thermodynamics of quantum systems. To illustrate the effectiveness of our approach, we apply it to compute the number of states of the 1D transverse-field Ising model and, consequently, its specific heat.
Quasiperiodic systems extend the concept of Anderson transition to the quasi-random and low-dimensional realm, exhibiting intricate behaviors even in the one-dimension, while their investigation in higher dimensions remains less explored. Here, we delve into a series of two-dimensional lattice models of Hall systems with asymptotically incommensurate flux, and reveal the impact of asymptotic incommensurability on transport phenomena. Specifically, we demonstrate anomalous bulk transport with universal scaling characteristics in the wave-packet dynamics and conductivity, and predict novel interplay effects involving asymptotic incommensurability, temperature, and relaxation, leading to unprecedented multiple anisotropic metal-insulator transitions. Furthermore, the quasiperiodicity also induces nontrivial anisotropy in edge transport when the system is fully insulating in one direction. Our work enriches the fundamental mechanisms underlying the metal-insulator transitions with anomalous bulk and edge transport driven by incommensurability in higher dimension, potentially opening an intriguing avenue for exploring novel transport phenomena in quasiperiodic systems.
Quantum multiprover interactive proof systems with entanglement MIP* are much more powerful than their classical counterpart MIP (Babai et al. '91, Ji et al. '20): while MIP = NEXP, the quantum class MIP* is equal to RE, a class including the halting problem. This is because the provers in MIP* can share unbounded quantum entanglement. However, recent works of Qin and Yao '21 and '23 have shown that this advantage is significantly reduced if the provers' shared state contains noise. This paper attempts to exactly characterize the effect of noise on the computational power of quantum multiprover interactive proof systems. We investigate the quantum two-prover one-round interactive system MIP*[poly, O(1)], where the verifier sends polynomially many bits to the provers and the provers send back constantly many bits. We show noise completely destroys the computational advantage given by shared entanglement in this model. Specifically, we show that if the provers are allowed to share arbitrarily many EPR states, where each EPR state is affected by an arbitrarily small constant amount of noise, the resulting complexity class is contained in NEXP = MIP. This improves significantly on the previous best-known bound of NEEEXP (nondeterministic triply exponential time) by Qin and Yao '21. We also show that this collapse in power is due to the noise, rather than the O(1) answer size, by showing that allowing for noiseless EPR states gives the class the full power of RE = MIP*[poly, poly]. Along the way, we develop two technical tools of independent interest. First, we give a new, deterministic tester for the positivity of an exponentially large matrix, provided it has a low-degree Fourier decomposition in terms of Pauli matrices. Secondly, we develop a new invariance principle for smooth matrix functions having bounded third-order Fr\'echet derivatives or which are Lipschitz continous.
Quantum mechanics imposes limits on the values of certain observables. Perhaps the most famous example is the uncertainty principle. Similar trade-offs also exist for simultaneous violation of multiple Bell inequalities. In the simplest case of three observers it has been shown that violation of one Bell inequality precludes any violation of other inequalities, a property called monogamy of Bell violations. Forms of Bell monogamy have been linked to the no-signalling principle and the inability of simultaneous violations of all inequalities is regarded as their fundamental characteristics. Here we show that Bell monogamy does not hold universally and in fact the only monogamous situation is that of three observers. Consequently, the nature of quantum nonlocality is truly polygamous. We present a systematic methodology for identifying quantum states and tight Bell inequalities that do not obey the monogamy principle for any number of more than three observers. The identified polygamous inequalities can be violated in state of the art setups and may be exploited for simultaneous self-testing of multiple stations in a quantum network.
Free-electron radiation phenomena are treated almost exclusively with classical electrodynamics, despite the intrinsic interaction being that of quantum electrodynamics. The lack of quantumness arises from the vast disparity between the electron energy and the much smaller photon energy, creating a small cross-section that makes quantum effects negligible. Here we identify a fundamentally distinct phenomenon of electron radiation that bypasses this energy disparity, and thus displays extremely strong quantum features. This phenomenon arises from free-electron elastic recoil, which can influence fundamental radiation processes in ways thought so far to necessitate inelastic scattering. The underlying reason for the quantum radiation features, which have no counterparts in classical theory, is the entanglement between each elastically recoiled electron and the photons it emitted. We show that this phenomenon is more accessible than all other types of quantum features in free-electron radiation and can be detected in current experimental setups such as electron microscopes. These quantum radiation features could guide the development of compact coherent X-ray sources facilitated by nanophotonics and quantum optics.
In this work we present an experimental demonstration of the Contextual Subspace Variational Quantum Eigensolver on superconducting quantum hardware. In particular, we compute the potential energy curve for molecular nitrogen, where a dominance of static correlation in the dissociation limit proves challenging for many conventional quantum chemistry techniques. Our quantum simulations retain good agreement with the full configuration interaction energy in the chosen STO-3G basis, outperforming coupled cluster singles doubles with perturbative triples as one stretches the triple bond past a separation of 1.73 {\AA}. To achieve this result we deploy a quantum error mitigation strategy made up of measurement-error mitigation, dynamical decoupling and zero-noise extrapolation, in addition to circuit parallelization that not only provides passive noise averaging but improves the effective shot yield to reduce the measurement overhead. Furthermore, we introduce a modification to previous adaptive ansatz construction algorithms that incorporates hardware-awareness.
Creating and manipulating quantum states of light requires nonlinear interactions, but while nonlinear optics is inherently multi-mode, quantum optical analyses are often done with single-mode approximations. We present a multi-mode theory for the transformation of a quantum pulse by Hamiltonians that are quadratic in the field creation and annihilation operators. Our theory describes nonlinear processes, such as parametric amplification and squeezing, as well as all linear processes, such as dispersion and beam splitting. We show that a single input pulse feeds only two distinct output modes and, for certain quantum states, just one. Our theory provides the quantum states in the output modes, which are crucial for the application of pulses in quantum optics and quantum information.
The emergence of quantum devices has raised a significant issue: how to certify the quantum properties of a device without placing trust in it. To characterise quantum states and measurements in a device-independent way, up to some degree of freedom, we can make use of a technique known as self-testing. While schemes have been proposed to self-test all pure multipartite entangled states and real local rank-one projective measurements, little has been done to certify mixed entangled states, composite or non-projective measurements. By employing the framework of quantum networks, we propose a scheme that can be used to self-test any quantum state, projective measurement and rank-one extremal non-projective measurements. The quantum network considered in this work is the simple star network, which is implementable using current technologies. For our purposes, we also construct a family of Bell inequalities that can be used to self-test the two-dimensional tomographically complete set of measurements with an arbitrary number of parties.
Integrated photonics has enabled countless technologies in telecommunications, spectroscopy, metrology, quantum optics, and quantum information processing. Using highly confined guided optical modes is the key that has made integrated circuits possible and has lead to scaling of complex designs, benefiting from their small footprint. At the same time, the field of quantum acoustics has recently gained significant attention due to its various potential advantages over its photonic counterparts, including smaller mode volume, lower energy, and orders of magnitude slower propagation speeds, as well as the potential for interconnecting distinct quantum systems. Developing analogous integrated phononic technology is critical for realizing the full potential of phonons and could lead to groundbreaking new applications, such as scalable quantum computing and hybrid quantum devices. In this work, we demonstrate for the first time a 4-port directional coupler for quantum mechanical excitations - a crucial component for integrated phononic circuits. Adjusting the length of the coupling region allows to realize phononic beam splitters with varying splitting ratios. By sending a single-phonon Fock state onto one of these phononic splitters, we demonstrate the capability of using the directional coupler directly in the quantum regime. Our work provides an essential step towards an integrated phononic platform for both classical and quantum technologies applications.
In this work, we develop a stochastic matrix product state (stoMPS) approach that combines the MPS technique and Monte Carlo samplings and can be applied to simulate quantum lattice models down to low temperature. In particular, we exploit a procedure to unbiasedly sample the local tensors in the matrix product states, which has one physical index of dimension $d$ and two geometric indices of dimension $D$, and find the results can be continuously improved by enlarging $D$. We benchmark the methods on small system sizes and then compare the results to those obtained with minimally entangled typical thermal states, finding that stoMPS has overall better performance with finite $D$. We further exploit the MPS sampling to simulate long spin chains, as well as the triangular and square lattices with cylinder circumference $W$ up to 4. Our results showcase the accuracy and effectiveness of stochastic tensor networks in finite-temperature simulations.
Bound states in the continuum (BICs) are quantum states with normalizable wave functions and energies that lie within the continuous spectrum for which extended or dispersive states are also available. These special states, which have shown great applicability in photonic systems for devices such as lasers and sensors, are also predicted to exist in electronic low-dimensional solid-state systems. The non-trivial topology of materials is within the known mechanisms that prevent the bound states to couple with the extended states. In this work we search for topologically protected BICs in a quantum Hall bar with an anti-dot formed by a pore far from the borders of the bar. The bound state energies and wavefunctions are calculated by means of the Recursive S-Matrix method. The resulting bound state energies coexist with extended states and exhibit a pattern complimentary to the Hofstadter butterfly. A symmetry-breaking diagonal disorder was introduced, showing that the BICs with energies far from the Landau levels remain robust. Moreover, the energy difference between consecutive BICs multiplied by the anti-dot perimeter follows the same curve despite disorder. Finally, a BIC-mediated current switching effect was found in a multi-terminal setup, which might permit their experimental detection.
We consider multileg ladders of Rydberg atoms which have been proposed as quantum simulators for the compact Abelian Higgs model (CAHM) in 1+1 dimensions [Y. Meurice, Phys. Rev. D 104, 094513 (2021)] and modified versions of theses simulators such as triangular prisms. Starting with the physical Hamiltonian for the analog simulator, we construct translation-invariant effective Hamiltonians by integrating over the simulator high-energy states produced by the blockade mechanism when some of the atoms are sufficiently close to each others. Remarkably, for all the simulators considered, the effective Hamiltonians have the three types of terms present for the CAHM (Electric field, matter charge and currents energies) but, in addition, terms quartic in the electric field. For the two leg ladder, these additional terms cannot be removed by fine-tuning the adjustable parameters of currently available devices. For positive detuning, the new terms create highly-degenerate vacua resulting in a very interesting phase diagram. Using numerical methods, we demonstrate the close correspondence between the physical simulator and the effective description for the ground state energy and real-time evolution. We discuss the phase diagram at fixed geometry with variable Rabi frequency and detuning and show that a rich variety of phases can be reached with potential interest in the context of QCD at finite density. We illustrate how the effective description can be used to design simulators with desirable properties from the point of view of constructing hybrid event generators.
Entanglement between massive particles is a purely quantum mechanical phenomenon with no counterpart in classical physics. Although polarized photons are suitable for applications of quantum entanglement over large distances, fundamental studies of entanglement in massive objects are often conducted for confined quantum systems, such as superconductors, quantum dots, and trapped ions. Here, we generate entanglement in a novel bipartite quantum system containing two massive objects: a photoelectron, which is a free particle propagating rapidly in space, and a light-dressed atomic ion with tunable coupled energy levels. Because of the entanglement, the measured photoelectron spectra reveal information about the coherent dynamics in the residual ion interacting with femtosecond extreme ultraviolet pulses delivered by a seeded free-electron laser. The observations are supported by a quantum optics based analytical model, which was further validated by numerical simulations based on the time-dependent Dirac equation. The degree of entanglement between the two objects is interpreted in terms of the entanglement entropy of the reduced system, as a function of the interaction time between the laser pulse and the dressed ion. Our results uncover the potential for using short-wavelength coherent light pulses from free-electron lasers to generate entangled photoelectron and ion systems for studying `spooky' action at a distance across ultrafast timescales.
Distributed quantum computing, particularly distributed quantum machine learning, has gained substantial prominence for its capacity to harness the collective power of distributed quantum resources, transcending the limitations of individual quantum nodes. Meanwhile, the critical concern of privacy within distributed computing protocols remains a significant challenge, particularly in standard classical federated learning (FL) scenarios where data of participating clients is susceptible to leakage via gradient inversion attacks by the server. This paper presents innovative quantum protocols with quantum communication designed to address the FL problem, strengthen privacy measures, and optimize communication efficiency. In contrast to previous works that leverage expressive variational quantum circuits or differential privacy techniques, we consider gradient information concealment using quantum states and propose two distinct FL protocols, one based on private inner-product estimation and the other on incremental learning. These protocols offer substantial advancements in privacy preservation with low communication resources, forging a path toward efficient quantum communication-assisted FL protocols and contributing to the development of secure distributed quantum machine learning, thus addressing critical privacy concerns in the quantum computing era.
Electrons in materials containing heavy elements are fundamentally relativistic and should in principle be described using the Dirac equation. However, the current standard for treatment of electrons in such materials involves density functional theory methods originally formulated from the Schr\"{o}dinger equation. While some extensions of the Schr\"{o}dinger-based formulation have been explored, such as the scalar relativistic approximation with or without spin-orbit coupling, these solutions do not provide a way to fully account for all relativistic effects of electrons, and the language used to describe such solutions are still based in the language of the Schr\"{o}dinger equation. In this article, we provide a different method for translating between the Dirac and Schr\"{o}dinger viewpoints in the context of a Coulomb potential. By retaining the Dirac four-vector notation and terminology in taking the non-relativistic limit, we see a much deeper connection between the Dirac and Schr\"{o}dinger equation solutions that allow us to more directly compare the effects of relativity in the angular and radial functions. Through this viewpoint, we introduce the concepts of densitals and Dirac spherical harmonics that allow us to translate more easily between the Dirac and Schr\"{o}dinger solutions. These concepts allow us to establish a useful language for discussing relativistic effects in materials containing elements throughout the full periodic table and thereby enable a more fundamental understanding of the effects of relativity on electronic structure.
The search for strategies to harness the temperature of quantum systems is one of the main goals in quantum thermodynamics. Here we study the dynamics of a system made of a pair of quantum harmonic oscillators, represented by single-mode cavity fields, interacting with a thermally excited beam of phaseonium atoms, which act as ancillas. The two cavities are arranged in a cascade configuration, so that the second cavity interacts with phaseonium atoms only after their interaction with the first one. We provide exact closed dynamics of the first cavity for arbitrarily long interaction times. We highlight the role played by the characteristic coherence phase of phaseonium atoms in determining the steady states of the cavity fields as well as that of the ancillas. Also, we show how the second cavity follows a non-Markovian evolution due to interactions with the "used" ancillary atoms, that enables information exchange with the first cavity. Adjusting the parameters of the phaseonium atoms, we can determine the final stable temperature reached by the cavities. In this way, the cavities can be heated up as well as cooled down. These results provide useful insights towards the use of different types of ancillas for thermodynamic cycles in cavity QED scenarios.
The Pancharatnam phase is a generalization of the Berry phase that applies to discrete sequences of quantum states. Here, we show that the Pancharatnam phase is a natural invariant for a wide class of quantum many-body dynamics involving measurements. We specifically investigate how a non-trivial Pancharatnam phase arises in the trajectories of Floquet quantum error-correcting codes and show that this phase can be extracted in a "computationally-assisted" interferometry protocol, involving additional post-processing based on the measurement record that defines a given quantum many-body trajectory. This Pancharatnam phase can also be directly related to the Berry phase accrued by continuous unitary evolution within a gapped phase. For the $\mathbb Z_2$ Floquet code of Hastings and Haah, we show that the associated family of unitary evolutions is the radical chiral Floquet phase. We demonstrate this correspondence explicitly by studying an exactly-solvable model of interacting spins.
We propose an efficient yet simple protocol to generate arbitrary symmetric entangled states with only global single-qubit rotations in a teared Hilbert space. The system is based on spin-1/2 qubits in a resonator such as atoms in an optical cavity or superconducting qubits coupled to a metal microwave resonator. By sending light or microwave into the resonator, it induces AC Stark shifts on particular angular-momentum eigenstates (Dicke states) of qubits. Then we are able to generate barriers that hinder transitions between adjacent Dicke states and tear the original Hilbert space into pieces. Therefore, a simple global single-qubit rotation becomes highly non-trivial, and thus generates entanglement among the many-body system. By optimal control of energy shifts on Dicke states, we are able to generate arbitrary symmetric entangled states. We also exemplify that we can create varieties of useful states with near-unity fidelities in only one or very few steps, including W states, spin-squeezed states (SSS), and Greenberger-Horne-Zeilinger (GHZ) states. Particularly, the SSS can be created by only one step with a squeezing parameter $\xi_R^2\sim1/N^{0.843}$ approaching the Heisenberg limit (HL). Our finding establishes a way for universal entanglement generations with only single-qubit drivings where all the multiple-qubit controls are integrated into simply switching on/off microwave. It has direct applications in the variational quantum optimizer which is available with existing technology.
We nearly triple the number of logical qubits per physical qubit of surface codes in the teraquop regime by concatenating them into high-density parity check codes. These "yoked surface codes" are arrayed in a rectangular grid, with parity checks (yokes) measured along each row, and optionally along each column, using lattice surgery. Our construction assumes no additional connectivity beyond a nearest neighbor square qubit grid operating at a physical error rate of $10^{-3}$.
We introduce a family of local models of dynamics based on ``word problems'' from computer science and group theory, for which we can place rigorous lower bounds on relaxation timescales. These models can be regarded either as random circuit or local Hamiltonian dynamics, and include many familiar examples of constrained dynamics as special cases. The configuration space of these models splits into dynamically disconnected sectors, and for initial states to relax, they must ``work out'' the other states in the sector to which they belong. When this problem has a high time complexity, relaxation is slow. In some of the cases we study, this problem also has high space complexity. When the space complexity is larger than the system size, an unconventional type of jamming transition can occur, whereby a system of a fixed size is not ergodic, but can be made ergodic by appending a large reservoir of sites in a trivial product state. This manifests itself in a new type of Hilbert space fragmentation that we call fragile fragmentation. We present explicit examples where slow relaxation and jamming strongly modify the hydrodynamics of conserved densities. In one example, density modulations of wavevector $q$ exhibit almost no relaxation until times $O(\exp(1/q))$, at which point they abruptly collapse. We also comment on extensions of our results to higher dimensions.
We present a Wave Operator Minimization (WOM) method for calculating the Fermi-Dirac density matrix for electronic structure problems at finite temperature while preserving physicality by construction using the wave operator, i.e., the square root of the density matrix. WOM models cooling a state initially at infinite temperature down to the desired finite temperature. We consider both the grand canonical (constant chemical potential) and canonical (constant number of electrons) ensembles. Additionally, we show that the number of steps required for convergence is independent of the number of atoms in the system. We hope that the discussion and results presented in this article reinvigorates interest in density matrix minimization methods.
Extended quantum networks are based on quantum repeaters that often rely on the distribution of entanglement in an efficient and heralded fashion over multiple network nodes. Many repeater architectures require multiplexed sources of entangled photon pairs, multiplexed quantum memories, and photon detection that distinguishes between the multiplexed modes. Here we demonstrate the concurrent employment of (1) spectrally multiplexed cavity-enhanced spontaneous parametric down-conversion in a nonlinear crystal; (2) a virtually-imaged phased array that enables mapping of spectral modes onto distinct spatial modes for frequency-selective detection; and (3) a cryogenically cooled Tm3+:LiNbO3 crystal that allows spectral filtering in an approach that anticipates its use as a spectrally-multiplexed quantum memory. Through coincidence measurements, we demonstrate quantum correlations between energy-correlated photon pairs and a strong reduction of the correlation strength between all other photons. This constitutes an important step towards a frequency multiplexed quantum repeater.
The concept of quantum representation of finite groups has been a fundamental aspect of quantum computing for quite some time, playing a role in every corner, from elementary quantum logic gates to the famous Shor's and Grover's algorithms. In this article, we provide a formal definition of this concept using both group theory and differential geometry. Our work proves the existence of a quantum representation for any finite group and outlines two methods for translating each generator of the group into a quantum circuit, utilizing gate decomposition of unitary matrices and variational quantum algorithms. Additionally, we provide numerical simulations of an explicit example on an open-access platform. Finally, we demonstrate the usefulness and potential of the quantum representation of finite groups by showing its role in the gate-level implementation of the algorithm that solves the hidden subgroup problem.
Nondeterministic measurement-based techniques are efficient in reshaping the population distribution of a quantum system but suffer from a limited success probability of holding the system in the target state. To reduce the experimental cost, we exploit the state-engineering mechanisms of both conditional and unconditional measurements and propose a two-step protocol assisted by a qubit to cool a resonator down to the ground state with a near-unit probability. In the first step, the unconditional measurements on the ancillary qubit are applied to reshape the target resonator from a thermal state to a reserved Fock state. The measurement sequence is optimized by reinforcement learning for a maximum fidelity. In the second step, the population on the reserved state can be faithfully transferred in a stepwise way to the resonator's ground state with a near-unit fidelity by the conditional measurements on the qubit. Intrinsic nondeterminacy of the projection-based conditional measurement is effectively inhibited by properly spacing the measurement sequence, which makes the Kraus operator act as a lowering operator for neighboring Fock states. Through dozens of measurements, the initial thermal average occupation of the resonator can be reduced by five orders in magnitude with a success probability over $95\%$.
Whereas the laser is nowadays an ubiquitous technology, applications for its microwave analogue, the maser, remain highly specialized, despite the excellent low-noise microwave amplification properties. The widespread application of masers is typically limited by the need of cryogenic temperatures. The recent realization of a continuous-wave room-temperature maser, using NV$^-$ centers in diamond, is a first step towards establishing the maser as a potential platform for microwave research and development, yet its design is far from optimal. Here, we design and construct an optimized setup able to characterize the operating space of a maser using NV$^-$ centers. We focus on the interplay of two key parameters for emission of microwave photons: the quality factor of the microwave resonator and the degree of spin level-inversion. We characterize the performance of the maser as a function of these two parameters, identifying the parameter space of operation and highlighting the requirements for maximal continuous microwave emission.
Indefinite causal order is an evolving field with potential involvement in quantum technologies. Here we propose and study one possible scenario of practical application in quantum communication: a compound entanglement distillation protocol that features two steps of a basic distillation protocol applied in a coherent superposition of two causal orders. This is achieved by using one faulty entangled pair to control-swap two others before a fourth pair is combined with the two swapped ones consecutively. As a result, the protocol distills the four faulty entangled states into one of a higher fidelity. Our protocol has a higher fidelity of distillation and probability of success for some input faulty pairs than conventional concatenations of the basic protocol that follow a definite distillation order. Our proposal shows the advantage of indefinite causal order in an application setting consistent with the requirements of quantum communication.
We propose an electrodynamic Aharonov-Bohm (AB) scheme where a nonzero AB phase difference appears even if the interferometer paths do not enclose a magnetic flux and are subjected to negligible scalar potential differences during the propagation of the quantum charged particle. In the proposal, the current in a solenoid outside the interferometer varies in time while the quantum particle is in a superposition state inside two Faraday cages, such that it is always subjected to negligible electromagnetic fields. At first glance, this result could challenge the topological nature of the AB effect. However, by considering the topology of the electromagnetic field configuration and the possible particle trajectories in spacetime, we demonstrate the topological nature of this situation.
We study measurement-induced symmetry-protected topological (SPT) order in a wide class of quantum random circuit models by combining calculations within the stabilizer formalism with tensor network simulations. We construct a family of quantum random circuits, generating the out-of-equilibrium version of all generalized cluster models, and derive a set of non-local string order parameters to distinguish different SPT phases. We apply this framework to investigate a random circuit realization of the XZX cluster model, and use the string order parameter to demonstrate that the phase diagram is stable against extending the class of unitary gates in the circuit, from Clifford gates to Haar unitaries. We then turn to the XZZX generalized cluster model, and demonstrate the coexistence of SPT order and spontaneous symmetry breaking, by relying on string order parameters and a connected correlation function.
Quantum transmission links are central elements in essentially all protocols involving the exchange of quantum messages. Emerging progress in quantum technologies involving such links needs to be accompanied by appropriate certification tools. In adversarial scenarios, a certification method can be vulnerable to attacks if too much trust is placed on the underlying system. Here, we propose a protocol in a device independent framework, which allows for the certification of practical quantum transmission links in scenarios where minimal assumptions are made about the functioning of the certification setup. In particular, we take unavoidable transmission losses into account by modeling the link as a completely-positive trace-decreasing map. We also, crucially, remove the assumption of independent and identically distributed samples, which is known to be incompatible with adversarial settings. Finally, in view of the use of the certified transmitted states for follow-up applications, our protocol moves beyond certification of the channel to allow us to estimate the quality of the transmitted quantum message itself. To illustrate the practical relevance and the feasibility of our protocol with currently available technology we provide an experimental implementation based on a state-of-the-art polarization entangled photon pair source in a Sagnac configuration and analyze its robustness for realistic losses and errors.
In lumped-element electrical circuit theory, the problem of solving Maxwell's equations in the presence of media is reduced to two sets of equations, the constitutive equations encapsulating local geometry and dynamics of a confined energy density, and the Kirchhoff equations enforcing conservation of charge and energy in a larger, topological, scale. We develop a new geometric and systematic description of the dynamics of general lumped-element electrical circuits as first order differential equations, derivable from a Lagrangian and a Rayleigh dissipation function. Through the Faddeev-Jackiw method we identify and classify the singularities that arise in the search for Hamiltonian descriptions of general networks. The core of our solution relies on the correct identification of the reduced manifold in which the circuit state is expressible, e.g., a mix of flux and charge degrees of freedom, including the presence of compact ones. We apply our fully programmable method to obtain (canonically quantizable) Hamiltonian descriptions of nonlinear and nonreciprocal circuits which would be cumbersome/singular if pure node-flux or loop-charge variables were used as a starting configuration space. This work unifies diverse existent geometrical pictures of electrical network theory, and will prove useful, for instance, to automatize the computation of exact Hamiltonian descriptions of superconducting quantum chips.
Spin anticoherent states acquired recently a lot of attention as the most "quantum" states. Some coherent and anticoherent spin states are known as optimal quantum rotosensors. In this work we introduce a measure of quantumness for orthonormal bases of spin states, determined by the average anticoherence of individual vectors and the Wehrl entropy. In this way we identify the most coherent and most quantum states, which lead to orthogonal measurements of extreme quantumness. Their symmetries can be revealed using the Majorana stellar representation, which provides an intuitive geometrical representation of a pure state by points on a sphere. Results obtained lead to maximally (minimally) entangled bases in the $2j+1$ dimensional symmetric subspace of the $2^{2j}$ dimensional space of states of multipartite systems composed of $2j$ qubits. Some bases found are iso-coherent as they consist of all states of the same degree of spin-coherence.
We demonstrate the simultaneous estimation of signal frequency and amplitude by a single quantum sensor in a single experimental shot. Sweeping the qubit splitting linearly across a span of frequencies induces a non-adiabatic Landau-Zener transition as the qubit crosses resonance. The signal frequency determines the time of the transition, and the amplitude its extent. Continuous weak measurement of this unitary evolution informs a parameter estimator retrieving precision measurements of frequency and amplitude. Implemented on radiofrequency-dressed ultracold atoms read out by a Faraday spin-light interface, we sense a magnetic signal with $20~\text{pT}$ precision in amplitude, and near-transform-limited precision in frequency, in a single $300~\text{ms}$ sweep from $7$ to $13~\text{kHz}$. The protocol realizes a swept-sine quantum spectrum analyzer, potentially sensing hundreds or thousands of channels with a single quantum sensor.
Quantum data access and quantum processing can make certain classically intractable learning tasks feasible. However, quantum capabilities will only be available to a select few in the near future. Thus, reliable schemes that allow classical clients to delegate learning to untrusted quantum servers are required to facilitate widespread access to quantum learning advantages. Building on a recently introduced framework of interactive proof systems for classical machine learning, we develop a framework for classical verification of quantum learning. We exhibit learning problems that a classical learner cannot efficiently solve on their own, but that they can efficiently and reliably solve when interacting with an untrusted quantum prover. Concretely, we consider the problems of agnostic learning parities and Fourier-sparse functions with respect to distributions with uniform input marginal. We propose a new quantum data access model that we call "mixture-of-superpositions" quantum examples, based on which we give efficient quantum learning algorithms for these tasks. Moreover, we prove that agnostic quantum parity and Fourier-sparse learning can be efficiently verified by a classical verifier with only random example or statistical query access. Finally, we showcase two general scenarios in learning and verification in which quantum mixture-of-superpositions examples do not lead to sample complexity improvements over classical data. Our results demonstrate that the potential power of quantum data for learning tasks, while not unlimited, can be utilized by classical agents through interaction with untrusted quantum entities.
The discovery of the backpropagation algorithm ranks among one of the most important moments in the history of machine learning, and has made possible the training of large-scale neural networks through its ability to compute gradients at roughly the same computational cost as model evaluation. Despite its importance, a similar backpropagation-like scaling for gradient evaluation of parameterised quantum circuits has remained elusive. Currently, the most popular method requires sampling from a number of circuits that scales with the number of circuit parameters, making training of large-scale quantum circuits prohibitively expensive in practice. Here we address this problem by introducing a class of structured circuits that are not known to be classically simulable and admit gradient estimation with significantly fewer circuits. In the simplest case -- for which the parameters feed into commuting quantum gates -- these circuits allow for fast estimation of the gradient, higher order partial derivatives and the Fisher information matrix. Moreover, specific families of parameterised circuits exist for which the scaling of gradient estimation is in line with classical backpropagation, and can thus be trained at scale. In a toy classification problem on 16 qubits, such circuits show competitive performance with other methods, while reducing the training cost by about two orders of magnitude.
The rapid development of quantum computing has led to increasing interest in quantum algorithms for a variety of different applications. Quantum walks have also experienced a surge in interest due to their potential use in quantum algorithms. Using the qiskit software package, we test how accurately the current generation of quantum computers provided by IBM can simulate a cycle discrete-time quantum walk. Implementing an 8-node, 8-step walk and a simpler 4-node, 4-step discrete-time quantum walk on an IBM quantum device known as ibmq_quito, the results for each step of the respective walks are presented. A custom noise model is developed in order to estimate that noise levels in the ibmq_santiago quantum device would need to be reduced by at least 94% in order to execute a 16-node, 16-step cycle discrete-time quantum walk to a reasonable level of fidelity.
A recent theoretical proposal for teleamplification requires preparation of Fock states, programmable interferometers, and photon-number resolving detectors to herald the teleamplification of an input state. These enable teleportation and heralded noiseless linear amplification of a photonic state up to an arbitrarily large energy cutoff. We report on adapting this proposal for Borealis and demonstrating teleamplification of squeezed-vacuum states with variable amplification factors. The results match the theoretical predictions and exhibit features of amplification in the teleported mode, with fidelities from 50 to 93%. This demonstration motivates the continued development of photonic quantum computing hardware for noiseless linear amplification's applications across quantum communication, sensing, and error correction.
We consider a rational six vertex model on a rectangular lattice with boundary conditions that generalize the usual domain wall type. We find that the partition function of the inhomogeneous version of this model is given by a modified Izergin determinant. The proofs are based on the quantum inverse scattering method and its representation theory together with elementary linear algebra.
Despite significant advancements in the field of quantum sciences over the past two decades, there remains a need for a quantum master equation that precisely and practically depicts quantum dynamics over long-time scales. In this study, we have effectively fulfilled this need by optimizing the computation process of the exact fourth-order time-convolutionless master equation. The earlier versions of this master equation required a three-dimensional integral to be computed, which limited their widespread usability. The master equation takes into account the fact that relaxation and dephasing can happen at the same time. This creates terms that are proportional to the derivative of the system's spectral density with frequency. These relaxation-dephasing hybrids are absent from second-order master equations and can lead to infrared divergent dynamics at zero temperature.
This paper introduces the ``comparison and replacement" (CNR) operation and propose a general-purposed pure quantum approximate algorithm for combinatorial optimization problems. The CNR operation can increase the probability of obtaining a string with high object function value. And our algorithm is constructed to a $p$-level divide-and-conquer structure with CNR operations to improve the quality of optimization. For a fixed size problem, the algorithm performance is improved with the increase of $p$ directly. And the algorithm performance in application converges to the theoretical case as the number of ancillary qubits $t$ increases. Furthermore, we demonstrate in theory and application that for sufficiently general combinatorial optimization problems, the algorithm can work and output a state with considerable approximation ratio. Moreover, the string with higher object function can be measured in the final state with higher probability. To put it further, we prove that the strings with the top $\frac{1}{2^p}$ object function value occupy the dominant probability(with lower bound around $1-\frac{1}{\mathrm{e}}\approx0.6321$) in final measurement after $p$-level algorithm. As an illustration, we show the results of our algorithm when applied to MAX-2-XOR instances and Gaussian weighted 2-edge graphs.
The Jordan-Wigner transformation is frequently utilised to rewrite quantum spin chains in terms of fermionic operators. When the resulting Hamiltonian is bilinear in these fermions, i.e. the fermions are free, the exact spectrum follows from the eigenvalues of a matrix whose size grows only linearly with the volume of the system. However, several Hamiltonians that do not admit a Jordan-Wigner transformation to fermion bilinears still have the same type of free-fermion spectra. The spectra of such ``free fermions in disguise" models can be found exactly by an intricate but explicit construction of the raising and lowering operators. We generalise the methods further to find a family of such spin chains. We compute the exact spectrum, and generalise an elegant graph-theory construction. We also explain how this family admits an N=2 lattice supersymmetry.
Estimation of quantum relative entropy and its R\'{e}nyi generalizations is a fundamental statistical task in quantum information theory, physics, and beyond. While several estimators of these divergences have been proposed in the literature along with their computational complexities explored, a limit distribution theory which characterizes the asymptotic fluctuations of the estimation error is still premature. As our main contribution, we characterize these asymptotic distributions in terms of Fr\'{e}chet derivatives of elementary operator-valued functions. We achieve this by leveraging an operator version of Taylor's theorem and identifying the regularity conditions needed. As an application of our results, we consider an estimator of quantum relative entropy based on Pauli tomography of quantum states and show that the resulting asymptotic distribution is a centered normal, with its variance characterized in terms of the Pauli operators and states. We utilize the knowledge of the aforementioned limit distribution to obtain asymptotic performance guarantees for a multi-hypothesis testing problem.
Motivated by limitations on the depth of near-term quantum devices, we study the depth-computation trade-off in the query model, where the depth corresponds to the number of adaptive query rounds and the computation per layer corresponds to the number of parallel queries per round. We achieve the strongest known separation between quantum algorithms with $r$ versus $r-1$ rounds of adaptivity. We do so by using the $k$-fold Forrelation problem introduced by Aaronson and Ambainis (SICOMP'18). For $k=2r$, this problem can be solved using an $r$ round quantum algorithm with only one query per round, yet we show that any $r-1$ round quantum algorithm needs an exponential (in the number of qubits) number of parallel queries per round. Our results are proven following the Fourier analytic machinery developed in recent works on quantum-classical separations. The key new component in our result are bounds on the Fourier weights of quantum query algorithms with bounded number of rounds of adaptivity. These may be of independent interest as they distinguish the polynomials that arise from such algorithms from arbitrary bounded polynomials of the same degree.
In a conducting medium held at finite temperature, free carriers are performing Brownian motion and generate fluctuating electromagnetic fields. We compute the averaged Lorentz force density that turns out nonzero in a thin sub-surface layer, pointing towards the surface, while vanishing in the bulk. This is an elementary example of rectified fluctuations, similar to the Casimir force or radiative heat transport. Our results also provide an experimental way to distinguish between the Drude and so-called plasma models.
We provide a systemic theory to entangle excitons with microcavity photons. This is realized by adopting an exciton-optomechanics system and introducing a nonlinear dispersive interaction with a mechanical oscillator. We show that when either the exciton and cavity modes in the weak-coupling regime, or the two exciton-polariton modes in the strong-coupling regime, are respectively resonant with the optomechanical Stokes and anti-Stokes sidebands, entanglement between excitons and cavity photons, or between two exciton polaritons, can be established. The entanglement is in the steady state and can potentially be achievable at room temperature. In both cases, genuine tripartite entanglement is shown to be present.
Reentrant localization (RL), a recently prominent phenomenon, traditionally links to the interplay of staggered correlated disorder and hopping dimerization, as indicated by prior research. Contrary to this paradigm, our present study demonstrates that hopping dimerization is not a pivotal factor in realizing RL. Considering a helical magnetic system with antiferromagnetic ordering, we uncover spin-dependent RL at multiple energy regions, in the {\em absence} of hopping dimerization. This phenomenon persists even in the thermodynamic limit. The correlated disorder in the form of Aubry-Andr\'{e}-Harper model is introduced by applying a transverse electric field to the helical system, circumventing the use of traditional substitutional disorder. Described within a tight-binding framework, present work provides a novel outlook on RL, highlighting the crucial role of electric field, antiferromagnetic ordering, and the helicity of the geometry.
Quantum light sources are crucial foundational components for various quantum technology applications. With the rapid development of quantum technology, there has been a growing demand for materials that are capable of hosting quantum emitters. One such material platform are fluorescent defects in hexagonal boron nitride (hBN) inducing deep sub-levels within the band gap. The question arises if other layered wide bandgap (2D) materials offer similar single photon emitting defects. Here, we investigate and compare the fabrication of quantum emitters in exfoliated multi-layer mica flakes with hBN and other wide bandgap 3D crystals (silicon carbide and gallium nitride) which are known to host quantum emitters. We use our primary fabrication technique of localized electron irradiation using a standard scanning electron microscope. To complement our experimental work, we employ density functional theory simulations to study the atomic structures of intrinsic defects and their photophysical properties. While our fabrication technique can create hBN quantum emitters with a high yield and high single photon purity, it is unable to fabricate emitters in the other solid-state crystals under investigation. This allows us to draw conclusions on the emitter fabrication mechanism, which could be relying on the activation of already present defects by charge state manipulation. We therefore provide an important step toward the identification of hBN emitters and their formation process.