Tuesdays 10:30 - 11:30 | Fridays 11:30 - 12:30
Showing votes from 2023-11-03 13:30 to 2023-11-07 11:30 | Next meeting is Friday Nov 1st, 11:30 am.
The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understanding of the Universe. Despite being sub-dominant to dark matter and dark energy, the baryonic component in our Universe holds substantial influence over the structure and mass of galaxy clusters. This paper presents a novel model to precisely quantify the impact of baryons on galaxy cluster virial halo masses, using the baryon fraction within a cluster as proxy for their effect. Constructed on the premise of quasi-adiabaticity, the model includes two parameters calibrated using non-radiative cosmological hydrodynamical simulations and a single large-scale simulation from the Magneticum set, which includes the physical processes driving galaxy formation. As a main result of our analysis, we demonstrate that this model delivers a remarkable one percent relative accuracy in determining the virial dark matter-only equivalent mass of galaxy clusters, starting from the corresponding total cluster mass and baryon fraction measured in hydrodynamical simulations. Furthermore, we demonstrate that this result is robust against changes in cosmological parameters and against varying the numerical implementation of the sub-resolution physical processes included in the simulations. Our work substantiates previous claims about the impact of baryons on cluster cosmology studies. In particular, we show how neglecting these effects would lead to biased cosmological constraints for a Euclid-like cluster abundance analysis. Importantly, we demonstrate that uncertainties associated with our model, arising from baryonic corrections to cluster masses, are sub-dominant when compared to the precision with which mass-observable relations will be calibrated using Euclid, as well as our current understanding of the baryon fraction within galaxy clusters.
Detailed modelling of the evolution of neutral hydrogen in the intergalactic medium during the Epoch of Reionization, $5 \leq z \leq 20$, is critical in interpreting the cosmological signals from current and upcoming 21-cm experiments such as Low-Frequency Array (LOFAR) and the Square Kilometre Array (SKA). Numerical radiative transfer codes offer the most physically motivated approach for simulating the reionization process. However, they are computationally expensive as they must encompass enormous cosmological volumes while accurately capturing astrophysical processes occurring at small scales ($\lesssim\rm Mpc$). Here, we present pyC$^2$Ray, an updated version of the massively parallel ray-tracing and chemistry code, C$^2$Ray, which has been extensively employed in reionization simulations. The most time-consuming part of the code is calculating the hydrogen column density along the path of the ionizing photons. Here, we present the Accelerated Short-characteristics Octhaedral RAytracing (ASORA) method, a ray-tracing algorithm specifically designed to run on graphical processing units (GPUs). We include a modern Python interface, allowing easy and customized use of the code without compromising computational efficiency. We test pyC$^2$Ray on a series of standard ray-tracing tests and a complete cosmological simulation with volume size $(349\,\rm Mpc)^3$, mesh size of $250^3$ and approximately $10^6$ sources. Compared to the original code, pyC$^2$Ray achieves the same results with negligible fractional differences, $\sim 10^{-5}$, and a speedup factor of two orders of magnitude. Benchmark analysis shows that ASORA takes a few nanoseconds per source per voxel and scales linearly for an increasing number of sources and voxels within the ray-tracing radii.
We study gauge preheating following pseudoscalar-driven inflation in full general relativity. We implement the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) scheme to solve the full nonlinear evolution of the metric alongside the dynamics of the pseudoscalar and gauge fields. The dynamics of the background and emission of gravitational waves are broadly consistent with simulations in a Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) spacetime. We find large, localized overdensities in the BSSN simulations of order $\delta = \delta\rho/\rho \sim 30$, and the dimensionless power spectrum of $\delta$ peaks above unity. These overdense regions are seeded on length scales only slightly smaller than the horizon, and have a compactness $C \sim 0.1$. The scale of peak compactness is shorter than the Jeans length, which implies that pressure of the matter fields plays an important role in the evolution of these objects.
We present {\sc slick} (the Scalable Line Intensity Computation Kit), a software package that calculates realistic CO, [\ion{C}{1}], and [\ion{C}{2}] luminosities for clouds and galaxies formed in hydrodynamic simulations. Built on the radiative transfer code {\sc despotic}, {\sc slick} computes the thermal, radiative, and statistical equilibrium in concentric zones of model clouds, based on their physical properties and individual environments. We validate our results applying {\sc slick} to the high-resolution run of the {\sc Simba} simulations, testing the derived luminosities against empirical and theoretical/analytic relations. To simulate the line emission from a universe of emitting clouds, we have incorporated random forest machine learning (ML) methods into our approach, allowing us to predict cosmologically evolving properties of CO, [\ion{C}{1}] and [\ion{C}{2}] emission from galaxies such as luminosity functions. We tested this model in 100,000 gas particles, and 2,500 galaxies, reaching an average accuracy of $\sim$99.8\% for all lines. Finally, we present the first model light cones created with realistic and ML-predicted CO, [\ion{C}{1}], and [\ion{C}{2}] luminosities in cosmological hydrodynamical simulations, from $z=0$ to $z=10$.
Aims. We study the possibility that the gas in cool-core clusters of galaxies has non-negligible rotation support, the impact of gas rotation on mass estimates from current X-ray observations, and the ability of forthcoming X-ray observatories to detect such rotation. Methods. We present three representative models of massive cool-core clusters with rotating intracluster medium (ICM) in equilibrium in cosmologically motivated spherical, oblate or prolate dark matter halos. In the models, the gas follows a composite-polytropic distribution, and has rotation velocity profiles consistent with current observational constraints. We show that the models are consistent with the available measurements of the ICM properties of the massive cluster population: thermodynamic profiles, shape of surface-brightness distribution, hydrostatic mass bias and broadening of X-ray emitting lines. Using the configuration for the microcalorimeter onboard the XRISM satellite, we generate a set of mock X-ray spectra of our cluster models, which we then analyze to make predictions on the estimates of the rotation speed that will be obtained with such an instrument. We then assess what fraction of the hydrostatic mass bias of our models could be accounted for by detecting rotation speed with XRISM spectroscopy over the range (0.1-1)r500. Results. Current data leave room for rotating ICM in cool-core clusters with peaks of rotation speed as high as 600 km/s. We have shown that such rotation, if present, will be detected with upcoming X-ray facilities such as XRISM and that 60-70% of the hydrostatic mass bias due to rotation can be accounted for using the line-of-sight velocity measured from X-ray spectroscopy with XRISM, with a residual bias smaller than 3% at an overdensity of 500. In this way, XRISM will allow us to pin down any mass bias of origin different from rotation.
We provide new constraints on the dark matter halo density profile of Milky Way (MW) dwarf spheroidal galaxies (dSphs) using the phase-space distribution function (DF) method. After assessing the systematics of the approach against mock data from the Gaia Challenge project, we apply the DF analysis to the entire kinematic sample of well-measured MW dwarf satellites for the first time. Contrary to previous findings for some of these objects, we find that the DF analysis yields results consistent with the standard Jeans analysis. In particular, in the present study we rediscover: i) a large diversity in the inner halo densities of dSphs (bracketed by Draco and Fornax), and ii) an anti-correlation between inner halo density and pericenter distance of the bright MW satellites. Regardless of the strength of the anti-correlation, we find that the distribution of these satellites in density vs. pericenter space is inconsistent with the results of the high-res N-body simulations that include a disk potential. Our analysis motivates further studies on the role of internal feedback and dark matter microphysics in these dSphs.
Black holes can amplify incoming bosonic waves via rotational superradiance, inducing bound states of ultralight bosons around them. This phenomenon has the potential to confine the parameter spaces of new bosons. Axions and axion-like particles (ALPs) are candidate beyond-standard-model particles that can form such clouds around supermassive black holes (SMBHs) and impact the polarization signal in a similar fashion to Faraday rotation via axion-photon coupling. Prior efforts have used polarized images from the Event Horizon Telescope (EHT) M87 2017 observations to limit the dimensionless axion-photon coupling to previously unexplored regions. However, with the novel calibration-insensitive quantities, closure traces and conjugate closure trace products, it is possible to constrain the existence of axion clouds while avoiding the dominant sources of systematic uncertainties, e.g., station gains and polarization leakages. We utilize a simple geometric model for the polarization map of M87* to fit the model parameters with both simulated and real data sets and reach a comparable level of constraint in the accuracy with which an axion cloud may be excluded in M87. Future applications of our approach include subsequent M87* and Sgr A* observations by EHT and next-generation EHT (ngEHT) are expected to produce stronger constraints across a wider range of axion and ALP masses. Because it does not require imaging, closure trace analyses may be applied to target AGN for which imaging is marginal, extending the number of SMBHs from which axion limits may be obtained significantly.
Deep learning models have been shown to outperform methods that rely on summary statistics, like the power spectrum, in extracting information from complex cosmological data sets. However, due to differences in the subgrid physics implementation and numerical approximations across different simulation suites, models trained on data from one cosmological simulation show a drop in performance when tested on another. Similarly, models trained on any of the simulations would also likely experience a drop in performance when applied to observational data. Training on data from two different suites of the CAMELS hydrodynamic cosmological simulations, we examine the generalization capabilities of Domain Adaptive Graph Neural Networks (DA-GNNs). By utilizing GNNs, we capitalize on their capacity to capture structured scale-free cosmological information from galaxy distributions. Moreover, by including unsupervised domain adaptation via Maximum Mean Discrepancy (MMD), we enable our models to extract domain-invariant features. We demonstrate that DA-GNN achieves higher accuracy and robustness on cross-dataset tasks (up to $28\%$ better relative error and up to almost an order of magnitude better $\chi^2$). Using data visualizations, we show the effects of domain adaptation on proper latent space data alignment. This shows that DA-GNNs are a promising method for extracting domain-independent cosmological information, a vital step toward robust deep learning for real cosmic survey data.
In this paper we introduce the software package ProPane, written for the R data analysis language. ProPane combines the full range of wcslib projections with the C++ image manipulation routines provided by the CImg library. ProPane offers routines for image warping and combining (including stacking), and various related tasks such as image alignment tweaking and pixel masking. It can stack an effectively unlimited number of target frames using multiple parallel cores, and offers threading for many lower level routines. It has been used for a number of current and upcoming large surveys, and we present a range of its capabilities and features. ProPane is already available under a permissive open-source LGPL-3 license at github.com/asgr/ProPane (DOI: 10.5281/zenodo.10057053).
We show how to use the cubic-quintic Gross-Pitaevskii-Poisson equation (cq-GPPE) and the cubic-quintic Stochastic Ginzburg-Landau-Poisson equation (cq-SGLPE) to investigate the gravitational collapse of a tenuous axionic gas into a collapsed axionic condensate for both zero and finite temperature $T$. At $T=0$, we use a Gaussian Ansatz for a spherically symmetric density to obtain parameter regimes in which we might expect to find compact axionic condensates. We then go beyond this Ansatz, by using the cq-SGLPE to investigate the dependence of the axionic condensate on the gravitational strength $G$ at $T = 0$. We demonstrate that, as $G$ increases, the equilibrium configuration goes from a tenuous axionic gas, to flat sheets or $\textit{Zeldovich pancakes}$, cylindrical structures, and finally a spherical axionic condensate. By varying $G$, we show that there are first-order phase transitions, as the system goes from one of these structures to the next one; we find hysteresis loops that are associated with these transitions. We examine these states and the transitions between these states via the Fourier truncated cq-GPPE; and we also obtain the thermalized $T > 0$ states from the cq-SGLPE; the transitions between these states yield thermally driven first-order phase transitions and their associated hysteresis loops. Finally, we discuss how our cq-GPPE approach can be used to follow the spatiotemporal evolution of a rotating axionic condensate and also a rotating binary-axionic-condensate system; in particular, we demonstrate, in the former, the emergence of vortices at large angular speeds $\Omega$ and, in the latter, the rich dynamics of the mergers of the components of this binary system, which can yield vortices in the process of merging.
We show that a mass-varying neutrino model driven by scalar field dark energy relaxes the existing upper bound on the current neutrino mass to ${\sum m_\nu < 0.72}$ eV. We extend the standard $\Lambda$CDM model by introducing two parameters: the rate of change of the scalar field with the number of $e$-folds and the coupling between neutrinos and the field. We investigate how they affect the matter power spectrum, the CMB anisotropies and its lensing potential. The model is tested against Planck observations of temperature, polarization, and lensing, combined with BAO measurements that constrain the background evolution. The results indicate that small couplings favor a cosmological constant, while larger couplings favor a dynamical dark energy, weakening the upper bound on current neutrino masses.
In the quest for the faint primordial B-mode polarization of the Cosmic Microwave Background, three are the key requirements for any present or future experiment: an utmost sensitivity, excellent control over instrumental systematic effects and over Galactic foreground contamination. Bolometric Interferometry (BI) is a novel technique that matches them all by combining the sensitivity of bolometric detectors, the control of instrumental systematics from interferometry and a software-based, tunable, in-band spectral resolution due to its ability to perform band-splitting during data analysis (spectral imaging). In this paper, we investigate how the spectral imaging capability of BI can help in detecting residual contamination in case an over-simplified model of foreground emission is assumed in the analysis. To mimic this situation, we focus on the next generation of ground-based CMB experiment, CMB-S4, and compare its anticipated sensitivities, frequency and sky coverage with a hypothetical version of the same experiment based on BI, CMB-S4/BI, assuming that line-of-sight (LOS) frequency decorrelation is present in dust emission but is not accounted for during component separation. We show results from a Monte-Carlo analysis based on a parametric component separation method (FGBuster), highlighting how BI has the potential to diagnose the presence of foreground residuals in estimates of the tensor-to-scalar ratio $r$ in the case of unaccounted Galactic dust LOS frequency decorrelation.
We have received a new physical characteristics fitting based on actual observational data from the Swift mission's long-duration gamma-ray bursts (LGRBs). We considered such characteristics as the Amati parameters for linear correlation ($E_\text{iso}-E_{\text{p},i}$) and the $k$-correction for gravitational lensing and Malmquist bias (GLMB) effect. We used the Pantheon SN Ia catalogue and the standard $\Lambda$CDM model with a fixed Hubble constant of $H_0=70$ km/s/Mpc as the baseline for the Hubble function $\mu(z)$. In our paper, we formulated the inverse cosmological calibration problem (ICCP) in the non-parametric statistics framework. The ICCP involves fitting non-observable physical characteristics while assuming a fixed cosmological model. To solve this problem, we developed a new method that is resistant to non-Gaussian processes. This method is based on error propagation through the Monte Carlo method and the Theil-Sen method for linear regression estimate. We have demonstrated the stability and robustness of this assessment method. The parameter estimates are as follows: $a=0.92^{+0.12}_{-0.12}$, $b=50.32^{+0.33}_{-0.32}$ without considering the GLMB effect, and $a=0.63^{+0.13}_{-0.14}$, $b=50.12^{+0.33}_{-0.31}$, and $k=1.98^{+0.25}_{-0.24}$ with the effect included. The proposed method can be applied to any other calibration sample of known standard candles, a calibrated sample of LGRBs, and the Hubble function $\mu(z)$. In the future, the ICCP idea can be used as an alternative cosmological test for estimating cosmological parameters, including the GLMB effect, or even for the selection of models, providing new information about the Universe. This can be done by analysing the residual values of observational data within the Bayesian statistics paradigm.
Inspired by a exponential $f(R)$ gravity model studied in the literature, in this work we introduce a new and viable $f(Q)$ gravity model, which can be represented as a perturbation of $\Lambda$CDM. Typically, within the realm of $f(Q)$ gravity, the customary approach to investigate cosmological evolution involves employing a parametrization of the Hubble expansion rate in terms of redshift, $H(z)$, among other strategies. In this work we have implemented a different strategy, deriving an analytical approximation for $H(z)$, from which we deduce approximated analytical expressions for the parameters $w_{\rm{DE}}$, $w_{\rm{eff}}$, and $\Omega_{\rm{DE}}$, as well as the deceleration parameter $q$. In order to verify the viability of this approximate analytical solution, we examined the behavior of the these parameters in the late-time regime. We find that for $b>0$, $w_{\rm{DE}}$ shows a quintessence-like behavior, while for $b<0$, it shows a phantom-like behavior. However, regardless of the sign of $b$, $w_{\rm{eff}}$ exhibits a quintessence-like behavior. Furthermore, it has been deduced that as the magnitude of the parameter $b$ increases, the present model deviates progressively from $\Lambda$CDM. We perform a Markov Chain Monte Carlo statistical analysis to test the model predictions with the Hubble parameter, the Pantheon supernova (SN) observational data, and the combination of those samples, obtaining constraints on the parameters of the model and the current values of the Hubble parameter and the matter density. Our findings indicate that this $f(Q)$ gravity model is indeed a viable candidate for describing the late-time evolution of the Universe at the background level.
Our aim is to combine data on single galaxies, galaxy groups, their BGGs, and their location in the cosmic web, to determine classes of groups, and to obtain a better understanding of their properties and evolution. Data on groups and their BGGs are based on the Sloan Digital Sky Survey DR10 MAIN spectroscopic galaxy sample. We characterize the group environments by the luminosity-density field and their filament membership. We divide BGGs according to their star formation properties as quenched, and red and blue star-forming galaxies. We apply multidimensional Gaussian mixture modelling to divide groups based on their properties and environments. We analyse the offset of BGGs with respect to the group centre, and the relation between the stellar velocity dispersion of BGGs and the group velocity dispersions. We show that the groups in our sample can be divided into two main classes: high-luminosity rich groups and clusters, and low-luminosity poor groups with threshold luminosity $L = 15 \times 10^{10} h^{-2} L_{sun}$ and mass $M = 23 \times 10^{12} h^{-1} M_{sun}$. In rich clusters approximately 90% of the BGGs are red and quenched galaxies, while in poor groups only 40- 60$% of BGGs are red and quenched, and the rest of the BGGs are star-forming, either blue (20 - 40% of BGGs) or red (17% of BCGs). Rich groups and clusters are located in global high-density regions in filaments or filament outskirts, while poor groups reside everywhere in the cosmic web. Our results suggest that group and cluster properties are modulated by their location in the cosmic web, but the properties of their BGGs are mostly determined by processes within group or cluster dark matter halo. We emphasize the role of superclusters as a special environment for group growth.
The Hawking evaporation of primordial black holes (PBH) reheats the Universe locally, forming hot spots that survive throughout their lifetime. We propose to use the temperature profile of such hot spots to calculate the decay rate of metastable vacua in cosmology, avoiding inconsistencies inherent to the Hartle-Hawking or Unruh vacuum. We apply our formalism to the case of the electroweak vacuum stability and find that a PBH energy fraction $\beta > 7\times 10^{-80} (M/g)^{3/2}$ is ruled out for black holes with masses $0.8 g < M < 10^{15} g$.
We examine gravitational waves (GWs) emitted from axionic strings and domain walls (DWs) in the early universe using advanced 3D lattice simulations. Our study encompasses scenarios for domain wall numbers $N_{\rm DW}=1$ and $N_{\rm DW}>1$, which correspond to GWs primarily from strings and DWs, respectively. Simulations begin before the Peccei-Quinn (PQ) phase transition and conclude with the destruction of string-wall networks below the QCD energy scale, relevant to both QCD axions and axion-like particles (ALPs). For $N_{\rm DW}=1$, the GW energy density from axion strings appears undetectable for both QCD axions and ALPs. In contrast, for $N_{\rm DW}>1$, the GW spectrum is largely determined by the bias term's coefficient, with the QCD axion model predicting undetectable GW emissions, while the ALPs model allows for a detectable GW signal in the nano-Hertz to the kilo-Hertz frequency range.
Axion-like particles (ALPs) are a well-motivated dark matter candidate that solve some of the problems in the clustering of large scale structure in cosmology. ALPs are often described by a simplified quadratic potential to specify the dynamics of the axion field, and are included in cosmological analysis codes using a modified fluid prescription. In this paper we consider the extreme axion: a version of the axion with a high initial field angle that produces an enhancement (rather than a suppression) of structure on small scales around the Jeans length, which can be probed by measurements of clustering such as the eBOSS DR14 Ly-$\alpha$ forest. We present a novel method of modeling the extreme axion as a cosmological fluid, combining the Generalized Dark Matter model with the effective fluid approach presented in the \texttt{axionCAMB} software, as well as implementing a series of computational innovations to efficiently simulate the extreme axions. We find that for axion masses between $10^{-23} \text{ eV} \lesssim m_a \lesssim 10^{-22.5} \text{ eV}$, constraints on the axion fraction imposed by the eBOSS DR14 Ly-$\alpha$ forest can be significantly weakened by allowing them to be in the form of extreme axions with a starting angle between $\pi - 10^{-1} \lesssim \theta_0 \lesssim \pi - 10^{-2}$. This work motivates and enables a more robust hydrodynamical analysis of extreme axions in order to compare them to high-resolution Ly-$\alpha$ forest data in the future.
Gravitational waves induced by large primordial curvature fluctuations may result in a sizable stochastic gravitational wave background. Interestingly, curvature fluctuations are gradually generated by initial isocurvature fluctuations, which in turn induce gravitational waves. Initial isocurvature fluctuations commonly appear in multi-field models of inflation as well as in the formation of scattered compact objects in the very early universe, such as primordial black holes and solitons like oscillons and cosmic strings. Here we provide a review on isocurvature induced gravitational waves and its applications to dark matter and the primordial black hole dominated early universe.
We show that the minimal Type-I Seesaw mechanism can successfully account for the observed dark matter abundance in the form of a keV sterile neutrino. This population can be produced by the decay of the heavier neutral leptons, with masses above the Higgs mass scale, while they are in thermal equilibrium in the early Universe (freeze-in). Moreover, the implementation of the relevant phenomenological constraints (relic abundance, indirect detection and structure formation) on this model automatically selects a region of the parameter space featuring an approximate lepton number symmetry.
The Javalambre Photometric Local Universe Survey (J-PLUS) is a 12-band photometric survey using the 83-cm JAST telescope. Data Release 3 includes 47.4 million sources. J-PLUS DR3 only provides star-galaxy classification so that quasars are not identified from the other sources. Given the size of the dataset, machine learning methods could provide a valid alternative classification and a solution to the classification of quasars. Our objective is to classify J-PLUS DR3 sources into galaxies, stars and quasars, outperforming the available classifiers in each class. We use an automated machine learning tool called TPOT to find an optimized pipeline to perform the classification. The supervised machine learning algorithms are trained on the crossmatch with SDSS DR18, LAMOST DR8 and Gaia. We checked that the training set of about 660 thousand galaxies, 1.2 million stars and 270 thousand quasars is both representative and contain a minimal presence of contaminants (less than 1%). We considered 37 features: the twelve photometric bands with respective errors, six colors, four morphological parameters, galactic extinction with its error and the PSF relative to the corresponding pointing. With TPOT genetic algorithm, we found that XGBoost provides the best performance: the AUC for galaxies, stars and quasars is above 0.99 and the average precision is above 0.99 for galaxies and stars and 0.96 for quasars. XGBoost outperforms the classifiers already provided in J-PLUS DR3 and also classifies quasars.
Subsonic turbulence plays a major role in determining properties of the intra cluster medium (ICM). We introduce a new Meshless Finite Mass (MFM) implementation in OpenGadget3 and apply it to this specific problem. To this end, we present a set of test cases to validate our implementation of the MFM framework in our code. These include but are not limited to: the soundwave and Kepler disk as smooth situations to probe the stability, a Rayleigh-Taylor and Kelvin-Helmholtz instability as popular mixing instabilities, a blob test as more complex example including both mixing and shocks, shock tubes with various Mach numbers, a Sedov blast wave, different tests including self-gravity such as gravitational freefall, a hydrostatic sphere, the Zeldovich-pancake, and a $10^{15}M_{\odot}$ galaxy cluster as cosmological application. Advantages over SPH include increased mixing and a better convergence behavior. We demonstrate that the MFM-solver is robust, also in a cosmological context. We show evidence that the solver performs extraordinarily well when applied to decaying subsonic turbulence, a problem very difficult to handle for many methods. MFM captures the expected velocity power spectrum with high accuracy and shows a good convergence behavior. Using MFM or SPH within OpenGadget3 leads to a comparable decay in turbulent energy due to numerical dissipation. When studying the energy decay for different initial turbulent energy fractions, we find that MFM performs well down to Mach numbers $\mathcal{M}\approx 0.01$. Finally, we show how important the slope limiter and the energy-entropy switch are to control the behavior and the evolution of the fluids.
Modelling nonlinear structure formation is essential for current and forthcoming cosmic shear experiments. We combine the halo model reaction formalism, implemented in the REACT code, with the COSMOPOWER machine learning emulation platform, to develop and publicly release REACTEMU-FR, a fast and accurate nonlinear matter power spectrum emulator for $f(R)$ gravity with massive neutrinos. Coupled with the state-of-the-art baryon feedback emulator BCEMU, we use REACTEMU-FR to produce Markov Chain Monte Carlo forecasts for a cosmic shear experiment with typical Stage IV specifications. We find that the inclusion of highly nonlinear scales (multipoles between $1500\leq \ell \leq 5000$) only mildly improves constraints on most standard cosmological parameters (less than a factor of 2). In particular, the necessary modelling of baryonic physics effectively damps most constraining power on the sum of the neutrino masses and modified gravity at $\ell \gtrsim 1500$. Using an approximate baryonic physics model produces mildly improved constraints on cosmological parameters which remain unbiased at the $1\sigma$-level, but significantly biases constraints on baryonic parameters at the $> 2\sigma$-level.
We present $\gamma$-ray optical-depth calculations from a recently published extragalactic background light (EBL) model built from multiwavelength galaxy data from the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (HST/CANDELS). CANDELS gathers one of the deepest and most complete observations of stellar and dust emissions in galaxies. This model resulted in a robust derivation of the evolving EBL spectral energy distribution up to $z\sim 6$, including the far-infrared peak. Therefore, the optical depths derived from this model will be useful for determining the attenuation of $\gamma$-ray photons coming from high-redshift sources, such as those detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, and for multi-TeV photons that will be detected from nearby sources by the future Cherenkov Telescope Array. From these newly calculated optical depths, we derive the cosmic $\gamma$-ray horizon and also measure the expansion rate and matter content of the Universe including an assessment of the impact of the EBL uncertainties. We find $H_{0}=61.9$ $^{+2.9}_{-2.4}$ km s$^{-1}$ Mpc$^{-1}$ when fixing $\Omega_{m}=0.32$, and $H_{0}=65.6$ $^{+5.6}_{-5.0}$ km s$^{-1}$ Mpc$^{-1}$ and $\Omega_{m}=0.19\pm 0.07$, when exploring these two parameters simultaneously.
Galaxy-scale strongly lensed systems have been shown to provide a unique technique for exploring the underlying physics of dark matter at sub-galactic scales. In the past, much attention was given to detecting and studying individual haloes in a strong lens system. In addition to the subhaloes, line-of-sight haloes contribute significantly to the small perturbations in lensed images. In prior work, we demonstrated that these line-of-sight haloes imprint a distinctive anisotropic signature and hence give rise to a detectable non-zero parity-even quadrupole moment in the effective convergence field's two-point correlation function. In this study, we show that these line-of-sight haloes also produce a non-zero curl component of the effective deflection field with a parity-odd quadrupole moment of the two-point function. These multipole moments have the ability to statistically separate line-of-sight haloes from dark matter substructure. In this paper, we examine how these multipole moments evolve in the presence of warm dark matter and self-interacting dark matter in terms of central density evolution and dark matter halo abundance. Importantly, we show that these different multipole moments display exquisite sensitivity to both the amplitude and the velocity dependence of the dark matter self-interaction cross-section. Our approach opens the door for strong lensing observations to probe dark matter self-interaction over a broad range of relative velocities.
We show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent non-standard post-inflationary cosmology make blue-tilted inflationary gravitational waves (GW) compatible with the recent findings of nHz stochastic GW background by the pulsar-timing arrays (PTAs) for high reheating temperatures. The right-handed neutrino (RHN) mass scale has to be $\mathcal{O}(\rm GeV)$. Remarkably, such a scenario produces a correlated signature testable by the future LIGO run. In addition to contributing to the active neutrino masses, $\mathcal{O}(\rm GeV)$ RHNs generate baryon asymmetry of the universe via low-scale-leptogenesis. They can be searched for in collider experiments. Therefore, the recent detection by PTAs is not only exciting for GWs in the nHz range; it paves the way to test and constrain well-studied mechanisms, such as seesaws, with a low-frequency and a correlated measurement of high-frequency GW spectral features, complementary to particle physics searches.
The recent Chandra-JWST discovery of a quasar in the z = 10.1 galaxy UHZ1 reveals that accreting supermassive black holes (SMBHs) were already in place 470 million years after the Big Bang. The Chandra X-ray source detected in UHZ1 is a Compton-thick quasar with a bolometric luminosity of $L_{\rm bol}\sim5\times10^{45}\ \rm{erg\ s^{-1}},$ which corresponds to an estimated BH mass of $\sim4\times10^7 \ \rm{M_{\odot}}$ assuming accretion at the Eddington rate. JWST NIRCAM and NIRSpec data yield a stellar mass estimate for UHZ1 comparable to its BH mass. These characteristics are in excellent agreement with prior theoretical predictions for a unique class of transient, high-redshift objects, Over-massive Black Hole Galaxies [OBGs] by Natarajan et al. that harbor a heavy initial black hole seed that likely formed from the direct collapse of the gas. Based on the excellent agreement between the observed multi-wavelength properties of UHZ1 with theoretical model template predictions, suggests that UHZ1 is the first detected OBG candidate. Our assertion rests on multiple lines of concordant evidence between model predictions and the following observed properties of UHZ1: its X-ray detection and the estimated ratio of the X-ray flux to the IR flux that is consistent with theoretical expectations for a heavy initial BH seed; its high measured redshift of z = 10.1, as predicted for the transient OBG stage (9 < z< 12); the amplitude and shape of the detected JWST Spectral Energy Distribution (SED) between 1 - 5 microns, which is in very good agreement with simulated template SEDs for OBGs; and the extended JWST morphology of UHZ1 that is suggestive of a recent merger, also expected for the formation of transient OBGs. As the first OBG candidate, UHZ1 provides compelling evidence for the formation of heavy initial seeds from direct collapse in the early Universe.
We compute the gravitational wave (GW) spectrum sourced by the sound waves produced during a first-order phase transition in the radiation-dominated epoch. The correlator of the velocity field is evaluated in accordance with the sound shell model. In our derivation, we include the effects of the expansion of the Universe, which are relevant in particular for sourcing processes whose time duration is comparable with the Hubble time. Our results show a causal growth at small frequencies, $\Omega_{\rm GW} \sim k^3$, possibly followed by a linear regime $\Omega_{\rm GW} \sim k$ at intermediate $k$, depending on the phase transition parameters. Around the peak, we find a steep growth that approaches the $k^9$ scaling found within the sound shell model. The resulting bump around the peak of the GW spectrum may represent a distinctive feature of GWs produced from acoustic motion. Nothing similar has been observed for vortical (magneto)hydrodynamic turbulence. Nevertheless, we find that the $k^9$ scaling is less extended than expected in the literature, and it does not necessarily appear. The dependence on the duration of the source, $\delta \tau_{\rm fin}$, is quadratic at small frequencies $k$, and proportional to $\ln^2 (1 + \delta \tau_{\rm fin} H_*)$ for an expanding Universe. At frequencies around the peak, the growth is suppressed by a factor $\Upsilon = 1 - 1/(\tau_{\rm fin} {H}_*)$ that becomes linear when the GW source is short. We discuss in which cases the dependence on the source duration is linear or quadratic for stationary processes. This affects the amplitude of the GW spectrum, both in the causality tail and at the peak, showing that the assumption of stationarity is a very relevant one, as far as the GW spectral shape is concerned. Finally, we present a general semi-analytical template of the resulting GW spectrum, as a function of the parameters of the phase transition.
We examine implications of the weak gravity conjecture for the mechanisms for discharging cosmological constant via membrane nucleations. Once screening fluxes and membranes which source them enter, and weak gravity bounds are enforced, a generic de Sitter space \underline{must} be unstable. We show that when all the flux terms which screen and discharge the cosmological constant are dominated by quadratic and higher order terms, the bounds from weak gravity conjecture and naturalness lead toward anthropic outcomes. In contrast, when the flux sectors are dominated by linear flux terms, anthropics may be avoided, and the cosmological constant may naturally decay toward smallest possible values.
For space gravitational wave (GW) detection, arm locking is a proposal useful in decreasing the frequency noise of the laser sources for current developing space missions LISA and TAIJI/TIANQIN. In this paper, we study the application of arm locking to the Astronomical Middle-frequency Interferometric Gravitational Observatory (AMIGO) to decrease the frequency noise of laser sources. For AMIGO, the arm-locking technique can suppress the laser frequency noise by three orders of magnitude. The advantage of this is to make the auxiliary noise assignment for AMIGO easier and more relaxed. For the first-generation time-delay interferometry (TDI) configuration, the laser frequency noise contribution is already below the core noise contribution. For the simple Michelson TDI configuration (X0), the arm locking makes the acceleration-thrust scheme, the delay-line scheme, or the combined scheme easier to implement. Within a relatively short period of less than a day (compared to less than twenty days for LISA/TAIJI), the Doppler frequency pulling can be efficiently reduced to within $\pm$ 0.001 Hz and does not affect the mission duty cycle much.
Accreting supermassive black holes (SMBHs) located at the center of galaxies are typically surrounded by large quantities of gas and dust. The structure and evolution of this circumnuclear material can be studied at different wavelengths, from the submillimeter to the X-rays. Recent X-ray studies have shown that the covering factor of the obscuring material tends to decrease with increasing Eddington ratio, likely due to radiative feedback on dusty gas. Here we study a sample of 549 nearby (z<0.1) hard X-ray (14-195 keV) selected non-blazar active galactic nuclei (AGN), and use the ratio between the AGN infrared and bolometric luminosity as a proxy of the covering factor. We find that, in agreement with what has been found by X-ray studies of the same sample, the covering factor decreases with increasing Eddington ratio. We also confirm previous findings which showed that obscured AGN typically have larger covering factors than unobscured sources. Finally, we find that the median covering factors of AGN located in different regions of the column density-Eddington ratio diagram are in good agreement with what would be expected from a radiation-regulated growth of SMBHs.
There are now multiple direct probes of the region near black hole horizons, including direct imaging with the Event Horizon Telescope (EHT). As a result, it is now of considerable interest to identify what aspects of the underlying spacetime are constrained by these observations. For this purpose, we present a new formulation of an existing broad class of integrable, axisymmetric, stationary spinning black hole spacetimes, specified by four free radial functions, that makes manifest which functions are responsible for setting the location and morphology of the event horizon and ergosphere. We explore the size of the black hole shadow and high-order photon rings for polar observers, approximately appropriate for the EHT observations of M87*, finding analogous expressions to those for general spherical spacetimes. Of particular interest, we find that these are independent of the properties of the ergosphere, but does directly probe on the free function that defines the event horizon. Based on these, we extend the nonperturbative, nonparametric characterization of the gravitational implications of various near-horizon measurements to spinning spacetimes. Finally, we demonstrate this characterization for a handful of explicit alternative spacetimes.
Recent observations suggest a stronger confinement of cosmic rays (CRs) in certain astrophysical systems than predicted by current CR-transport theories. We posit that the incorporation of microscale physics into CR-transport models can account for this enhanced CR confinement. We develop a theoretical description of the effect of magnetic microscale fluctuations originating from the mirror instability on macroscopic CR diffusion. We confirm our theory with large-dynamical-range simulations of CR transport in the intracluster medium (ICM) of galaxy clusters and kinetic simulations of CR transport in micromirror fields. We conclude that sub-TeV CR confinement in the ICM is far more effective than previously anticipated on the basis of Galactic-transport extrapolations.
The detection of gravitational waves with Pulsar Timing Arrays (PTAs) requires precise measurement of the difference between the pulsars' timing models and their observed pulses, as well as dealing with numerous and sometimes hard to diagnose sources of noise. Outliers may have an impact on this already difficult procedure, especially if the methods used are not robust to such anomalous observations. Until now, no complete and practical quantification of their effects on PTA data has been provided. With this work, we aim to fill this gap. We corrupt simulated datasets featuring an increasing degree of complexity with varying percentages of uniformly distributed outliers and investigate the impact of the latter on the recovery of the injected gravitational wave signals and pulsar noise terms. We found that the gravitational waves signal, due to its expected correlation, is more robust against these anomalous observations when compared to the other injected processes. This result is especially relevant in the context of the emerging statistical evidence for the gravitational wave background in PTA datasets, further strengthening those claims.
We present preliminary results of the analysis of optical spectra of two complementary samples of Seyfert galaxies. The first sample was extracted from a selection of the 4th Fermi Gamma-ray Large Area Telescope (4FGL) catalog, and consists of 9 $\gamma$-ray emitting jetted Seyfert galaxies. The second one was extracted from the Swift-BAT AGN Spectroscopic Survey (BASS), and is composed of 38 hard-X ray selected Active Galactic Nuclei (AGN). These two samples are complementary, with the former expected to have smaller viewing angles, while the latter may include objects with larger viewing angles. We measured emission line ratios to investigate whether the behavior of these Seyferts can be explained in terms of obscuration, as suggested by the well-known Unified Model (UM) of AGN, or if there are intrinsic differences due to the presence of jets, outflows, or the evolution. We found no indications of intrinsic differences. The UM remains the most plausible interpretation for these classes of objects even if some results can be challenging for this model.
Gamma-ray bursts (GRBs) are one of the most promising transient events for studying multi-wavelength observations in extreme conditions. Observation of GeV photons from bursts would provide crucial information on GRB physics, including the off-axis emission. The Second Gamma-ray Burst Catalog (2FLGC) was announced by the Fermi Large Area Telescope (Fermi-LAT) Collaboration. This catalog includes 29 bursts with photon energy higher than 10 GeV. While the synchrotron forward-shock model has well explained the afterglow data of GRBs, photon energies greater than 10 GeV are very difficult to interpret within this framework. To study the spectral and temporal indices of those bursts described in 2FLGC, Fraija et al. (2022a) proposed the closure relations (CRs) of the synchrotron self-Compton (SSC) emitted from an on-axis jet which decelerates in stellar-wind and the constant-density medium. In this paper, we extend the CRs of the SSC afterglow from an on-axis scenario to an off-axis, including the synchrotron afterglow radiation that seems off-axis. In order to investigate the spectral and temporal index evolution of those bursts reported in 2FLGC, we consider the hydrodynamical evolution with energy injection in the adiabatic and radiative regime for an electron distribution with a spectral index of $1<p<2$ and $2 < p$. The results show that the most likely scenario for synchrotron emission corresponds to the stellar wind whether or not there is energy injection and that the most likely scenario for SSC emission corresponds to the constant density when there is no energy injection and to the stellar wind when there is energy injection.
The second {\itshape Fermi}/LAT gamma-ray burst (GRB) catalog (2FLGC) spanning the first decade of operations by the LAT collaboration was recently released. The closure relations of the synchrotron forward shock (FS) model are not able to reproduce a sizeable portion of the afterglow-phase light curves in this collection, indicating that there may be a large contribution from some other mechanism. Recently, synchrotron self-Compton (SSC) light curves from the reverse shock (RS) regions were derived in the thick- and thin-shell regime for a constant-density medium, and it was demonstrated that analytical light curves could explain the~GeV flare observed in several bursts from 2FLGC, including GRB 160509A. Here, we generalise the SSC RS scenario from the constant density to a stratified medium, and show that this contribution helps to describe the early light curves exhibited in some {\itshape Fermi}/LAT-detected bursts. As a particular case, we model a sample of eight bursts that exhibited a short-lasting emission with the synchrotron and SSC model from FS and RS regions, evolving in a stellar-wind environment, constraining the microphysical parameters, the circumburst density, the bulk Lorentz factor, and the fraction of shock-accelerated electrons. We demonstrate that the highest-energy photons can only be described by the SSC from the forward-shock region.
We present a comprehensive variability study on three blazars, S4 0954+65, PKS 0903-57, and 4C +01.02 covering a mass range of log(M/M$_{\odot}$) = 8--9, by using $\sim$15 years-long $\gamma$-ray light curves from \textit{Fermi}-LAT. The variability level is characterized by the fractional variability amplitude which is higher for $\gamma$-rays compared to optical/UV and X-rays emissions. A power spectral density (PSD) study and damped random walk (DRW) modeling are done to probe the characteristic timescale. The PSD is fitted with a single power-law (PL) and bending power-law models and the corresponding success fraction was estimated. In the case of PKS 0903-57, We observed a break in the $\gamma$-ray PSD at 256 days which is comparable to the viscous timescale in the accretion disc suggesting a possible disk-jet coupling. The non-thermal damping timescale from the DRW modeling is compared with the thermal damping timescale for AGNs including our three sources. Our sources lie on the best-fit of the $\mathrm{\tau^{rest}_{damping}} - M_{BH}$ plot derived for AGN suggesting a possible accretion disc-jet connection. If the jet's variability is linked to the disc's variability, we expect a log-normal flux distribution, often connected to the accretion disc's multiplicative processes. Our study observed a double log-normal flux distribution, possibly linked to long and short-term variability from the accretion disk and the jet. In summary, PSD and DRW modeling results for these three sources combined with blazars and AGNs studied in literature favor a disc-jet coupling scenario. However, more such studies are needed to refine this understanding.
We report the first time measurement of X-ray polarization in the 2$-$8 keV band from the high synchrotron peaked (HSP) blazar 1ES 1959+650. The low energy hump in the broadband spectral energy distribution (SED) of blazars in the log$\nu$ versus $\nu F_{\nu}$ plane is believed to be due to the synchrotron emission process from relativistic particles in their jets. In HSP blazars, the observed X-ray emission lies in the high energy tail of the synchrotron part of the SED, and X-ray polarization measurements can constrain the processes by which particles are accelerated in their jets. We present here our results on the X-ray polarization characteristics of 1ES 1959+650 using observations carried out by the {\it Imaging X-ray Polarimetry Explorer (IXPE)}. {\it IXPE} observed this source for four epochs between May 2022 and August 2023, with observation time ranging from about 50 to 300 ksec. Of the four epochs of observations, we detected polarization on two epochs, significantly larger than the minimum detectable polarization values. From model-independent analysis during the observations on 28 October 2022, in the 2$-$8 keV band, we found the degree of polarization of $\Pi_X$ = 9.0 $\pm$ 1.6 \% and an electric vector position angle of $\psi_X$ = 53 $\pm$ 5 deg. Similarly, from the observations on 14 August 2023, we found $\Pi_X$ and $\psi_X$ values as 12.5 $\pm$ 0.7 \% and 20 $\pm$ 2 deg respectively in the 2$-$8 keV band. These values obtained from model-independent analysis are also in agreement with the values obtained from spectro-polarimetric analysis of the I, Q, and U spectra in the 2$-$8 keV range. The measured X-ray polarization is larger than that known in the optical that ranges between 2.5$-$9\% during the period 2008 to 2018. This result can be inferred as the shock acceleration of the particles in the jet of 1ES 1959+650.
Young massive stars in compact stellar clusters could end their evolution as core-collapse supernovae a few million years after the cluster was built. The blast wave of a supernova propagates through the inner cluster region with multiple stellar winds of young luminous stars. We present the results of 3D magnetohydrodynamic simulations of the plasma flows produced by a supernova event inside a cluster with a population of massive stars similar to that in Westerlund 1. We followed its evolution over a few thousand years (i.e. a few shock crossing times). The plasma temperature, density and magnetic field, which are highly disturbed by supernova event, relax to values close to the initial over the studied period. The relaxation time of a cluster is a few thousand years, which is a sizeable fraction of the period between the successive supernova events for a massive cluster of a few million years age. The spectra of the cluster diffuse X-ray emission simulated here should be representative for the galactic and extragalactic young massive clusters. The resultant magnetic fields are highly intermittent, so we derived the volume filling factors for a set of magnetic field ranges. Highly amplified magnetic fields of magnitude well above 100 $\mu$G fill in a few per cent of the cluster volume, but still dominate the magnetic energy. The structure of the magnetic fields and high velocity plasma flows with shocks in the system are favorable for both proton and electron acceleration to energies well above TeV.
We explore the stimulated emission of photons in non-spherical axion clusters with or without the axion source from the superradiance of a rotating black hole (BH). In particular, we focus on the cluster with the initial axion distribution in the $(l,m)=(1,1)$ mode which mimics the shape of an axion cloud induced by the BH superradiance. After establishing the hierarchy of Boltzmann equations governing a general non-spherical axion-photon system, we examine the evolution of photon and axion distributions in the cluster and possible stimulated emission signals. In the case without the axion source, the resultant signal would be a large single photon pulse. As for the system with the BH superradiance as the axion source, multiple pulses of various amplitudes are predicted. We also show that, for the latter case, the combined effects of stimulated emissions and the axion production from the BH superradiance could reach a balance where the axion cluster becomes uniformly and spherically distributed. Due to the energy and temporal characteristics of the obtained pulses, we demonstrate that the stimulated emissions from the axion cluster with axions sourced by the BH superradiance provide a candidate explanation to the observed fast radio bursts.
A relevant fraction of massive stars are runaway stars. These stars move with a significant peculiar velocity with respect to their environment. We aim to discover and characterize the population of massive and early-type runaway stars in the GOSC and BeSS catalogs using Gaia DR3 astrometric data. We present a 2-dimensional method in the velocity space to discover runaway stars as those that deviate significantly from the velocity distribution of field stars, which are considered to follow the Galactic rotation curve. We found 106 O runaway stars, 42 of which were not previously identified as runaways. We found 69 Be runaway stars, 47 of which were not previously identified as runaways. The dispersion of runaway stars is a few times higher in Z and b than that of field stars. This is explained by the ejections they underwent when they became runaways. The percentage of runaways is 25.4% for O-type stars, and it is 5.2% for Be-type stars. In addition, we conducted simulations in 3 dimensions for our catalogs. They revealed that these percentages could increase to ~30% and ~6.7%, respectively. Our runaway stars include seven X-ray binaries and one gamma-ray binary. Moreover, we obtain velocity dispersions of ~5 km/s perpendicular to the Galactic plane for O- and Be-type field stars. These values increase in the Galactic plane to ~7 km/s for O-type stars due to uncertainties and to ~9 km/s for Be-type stars due to Galactic velocity diffusion. The excellent Gaia DR3 astrometric data have allowed us to identify a significant number of O-type and Be-type runaways in the GOSC and BeSS catalogs. The higher percentages and higher velocities found for O-type compared to Be-type runaways underline that the dynamical ejection scenario is more likely than the binary supernova scenario. Our results open the door to identifying new high-energy systems among our runaways by conducting detailed studies.
Gamma-ray emission provides constraints on the non-thermal radiation processes at play in astrophysical particle accelerators. This allows both the nature of accelerated particles and the maximum energy that they can reach to be determined. Notably, it remains an open question to what extent supernova remnants (SNRs) contribute to the sea of Galactic cosmic rays. In the Galactic plane, at around 312{\deg} of Galactic longitude, Fermi-LAT observations show an extended source (4FGL J1409.1-6121e) around five powerful pulsars. This source is described by one large disk of 0.7{\deg} radius with a high significance of 45 sigma in the 4FGL-DR3 catalog. Using 14 years of Fermi-LAT observations, we revisited this region with a detailed spectro-morphological analysis in order to disentangle its underlying structure. Three sources have been distinguished, including the supernova remnant G312.4-0.4 whose gamma-ray emission correlates well with the shell observed at radio energies. The hard spectrum detected by the LAT, extending up to 100 GeV without any sign of cut-off, is well reproduced by a purely hadronic model.
Supermassive black holes at the centre of active galactic nuclei power some of the most luminous objects in the Universe. Typically, very long baseline interferometric (VLBI) observations of blazars have revealed only funnel-like morphologies with little information of the ejected plasma internal structure, or lacked the sufficient dynamic range to reconstruct the extended jet emission. Here we show microarcsecond-scale angular resolution images of the blazar 3C 279 obtained at 22 GHz with the space VLBI mission RadioAstron, which allowed us to resolve the jet transversely and reveal several filaments produced by plasma instabilities in a kinetically dominated flow. Our high angular resolution and dynamic range image suggests that emission features traveling down the jet may manifest as a result of differential Doppler-boosting within the filaments, as opposed to the standard shock-in-jet model invoked to explain blazar jet radio variability. Moreover, we infer that the filaments in 3C 279 are possibly threaded by a helical magnetic field rotating clockwise, as seen in the direction of the flow motion, with an intrinsic helix pitch angle of ~45 degrees in a jet with a Lorentz factor of ~13 at the time of observation.
Massive stars play a major role in the evolution of their host galaxies, and serve as important probes of the distant Universe. It has been established that the majority of massive stars reside in close binaries and will interact with their companion stars during their lifetime. Such interactions drastically alter their life cycles and complicate our understanding of their evolution, but are also responsible for the production of interesting and exotic interaction products. - Extensive observation campaigns with well-understood detection sensitivities have allowed to convert the observed properties into intrinsic characteristics, facilitating a direct comparison to theory. - Studies of large samples of massive stars in our Galaxy and the Magellanic Clouds have unveiled new types of interaction products, providing critical constraints on the mass transfer phase and the formation of compact objects. - The direct detection of gravitational waves has revolutionized the study of stellar mass compact objects, providing a new window to study massive star evolution. Their formation processes are, however, still unclear. The known sample of compact object mergers will grow by orders of magnitude in the coming decade, turning into the best understood astrophysical population.
This is a brief, non-exhaustive review of Fast Radio Burst (FRB), a new category of radio transients originating from extragalactic distances. We discuss the key observational properties known so far and the scientific applications of FRBs. We summarize the FRB-related research in the French astrophysics community, and conclude by sharing some insights to the future of FRB science.
These notes cover part of the lectures presented by Andrea Maselli for the 59th Winter School of Theoretical Physics and third COST Action CA18108 Training School 'Gravity -- Classical, Quantum and Phenomenology'. The school took place at Palac Wojan\'ow, Poland, from February 12th to 21st, 2023. The lectures focused on some key aspects of black hole physics, and in particular on the dynamics of particles and on the scattering of waves in the Schwarzschild spacetime. The goal of the course was to introduce the students to the concept of black hole quasi normal modes, to discuss their properties, their connection with the geodesic motion of massless particles, and to provide numerical approaches to compute their actual values.
We present results from a long-term monitoring of frequency dependent eclipses of the radio emission from PSR J1544+4937 which is a ``black widow spider'' millisecond pulsar (MSP) in a compact binary system. The majority of such systems often exhibit relatively long duration radio eclipses caused by ablated material from their companion stars. With the wide spectral bandwidth of upgraded Giant Metrewave Radio Telescope (uGMRT), we present first systematic study of temporal variation of eclipse cut-off frequency. With decade-long monitoring of 39 eclipses for PSR J1544+4937, we notice significant changes in the observed cut-off frequency ranging from 343 $\pm$ 7 MHz to > 740 MHz. We also monitored changes in eclipse cut-off frequency on timescales of tens of days and observed a maximum change of $\ge$ 315 MHz between observations that were separated by 22 days. In addition, we observed a change of $\sim$ 47 MHz in eclipse cut-off frequency between adjacent orbits, i.e. on timescales of $\sim 2.9$ hours. We infer that such changes in the eclipse cut-off frequency depict an eclipse environment for the PSR J1544+4937 system that is dynamically evolving, where, along with the change in electron density, the magnetic field could also be varying. We also report a significant correlation between the eclipse cut-off frequency and the mass loss rate of the companion. This study provides the first direct evidence of mass loss rate affecting the frequency dependent eclipsing in a spider MSP.
We report low-frequency radio observations of the 2021 outburst of the recurrent nova RS Ophiuchi. These observations include the lowest frequency observations of this system to date. Detailed light curves are obtained by MeerKAT at 0.82 and 1.28 GHz and LOFAR at 54 and 154 MHz. These low-frequency detections allow us to put stringent constraints on the brightness temperature that clearly favour a non-thermal emission mechanism. The radio emission is interpreted and modelled as synchrotron emission from the shock interaction between the nova ejecta and the circumbinary medium. The light curve shows a plateauing behaviour after the first peak, which can be explained by either a non-uniform density of the circumbinary medium or a second emission component. Allowing for a second component in the light-curve modelling captures the steep decay at late times. Furthermore, extrapolating this model to 15 yr after the outburst shows that the radio emission might not fully disappear between outbursts. Further modelling of the light curves indicates a red giant mass-loss rate of $\sim 5 \cdot 10^{-8}~{\rm M_\odot~yr^{-1}}$. The spectrum cannot be modelled in detail at this stage, as there are likely at least four emission components. Radio emission from stellar wind or synchrotron jets is ruled out as the possible origin of the radio emission. Finally, we suggest a strategy for future observations that would advance our understanding of the physical properties of RS Ophiuchi.
By performing ideal magnetohydrodynamical (MHD) simulations with weak vertical magnetic fields in unstratified cylindrical shearing boxes with modified boundary treatment, we investigate MHD turbulence excited by magnetorotational instability. The cylindrical simulation exhibits extremely large temporal variation in the magnetic activity compared to the simulation in a normal Cartesian shearing box, although the time-averaged field strengths are comparable in the cylindrical and Cartesian setups. Detailed analysis of the terms describing magnetic-energy evolution with "triangle diagrams" surprisingly reveals that in the cylindrical simulation the compression of toroidal magnetic field is unexpectedly as important as the winding due to differential rotation in amplifying magnetic fields and triggering intermittent magnetic bursts, which are not seen in the Cartesian simulation. The importance of the compressible amplification is also true for a cylindrical simulation with tiny curvature; the evolution of magnetic fields in the nearly Cartesian shearing box simulation is fundamentally different from that in the exact Cartesian counterpart. The radial gradient of epicycle frequency, $\kappa$, which cannot be considered in the normal Cartesian shearing box model, is the cause of this fundamental difference. An additional consequence of the spatial variation of $\kappa$ is continuous and ubiquitous formation of narrow high(low)-density and weak(strong)-field localized structures; seeds of these ring-gap structures are created by the compressible effect and subsequently amplified and maintained under the marginally unstable condition regarding "viscous-type" instability.
We present the expected X-ray polarization signal resulting from distant reprocessing material around black holes. Using a central isotropic power-law emission at the center of the simulated model, we add distant equatorial and axially symmetric media that are covering the central accreting sources. We include partial ionization and partial transparency effects, and the impact of various polarization and steepness of the primary radiation spectrum. The results are obtained with the Monte Carlo code STOKES that considers both line and continuum processes and computes the effects of scattering and absorption inside static homogenous wedge-shaped and elliptical toroidal structures, varying in relative size, composition and distance to the source. We provide first order estimates for parsec-scale reprocessing in Compton-thin and Compton-thick active galactic nuclei, as well as winds around accreting stellar-mass compact objects, for observer's inclinations above and below the grazing angle. The resulting reprocessed polarization can reach tens of % with either parallel or perpendicular orientation with respect to the axis of symmetry, depending on subtle details of the geometry, density and ionization structure. We also show how principal parameters constrained from X-ray spectroscopy or polarimetry in other wavelengths can lift the shown degeneracies in X-ray polarization. We provide an application example of the broad modelling discussion by revisiting the recent IXPE 2-8 keV X-ray polarimetric observation of the accreting stellar-mass black hole in Cygnus X-3 from the perspective of partial transparency and ionization of the obscuring outflows.
Recently, the piercing of a mini boson star by a black hole was studied, with tidal capture and the discovery of a "gravitational atom" being reported ( arXiv:2206.00021 [gr-qc] ). Building on this research, we extend the study by including a hexic solitonic potential and explore the piercing of a solitonic boson star by a black hole. Notably, the solitonic boson star can reach higher compactness, which one might expect could alter the dynamics in this context. Our findings suggest that even when the black hole's size approaches the test particle limit, the solitonic boson star is easily captured by the black hole due to an extreme tidal capture process. Regardless of the black hole initial mass and velocity, our results indicate that over 85% of the boson star material is accreted. Thus, the self-interaction does not alter the qualitative behavior of the system.
We investigate neutrino non-radiative two-body decay in vacuum, in relation to SN1987A. In a full $3\nu$ decay framework, we perform a detailed likelihood analysis of the 24 neutrino events from SN1987A observed by Kamiokande-II, IMB, and Baksan. We consider both normal and inverted neutrino mass orderings, and the possibility of strongly hierarchical and quasi-degenerate neutrino mass patterns. The results of the likelihood analysis show that the sensitivity is too low to derive bounds in the case of normal mass ordering. On the contrary, in the case of inverted mass ordering we obtain the bound $\tau/m \ge 2.4 \times 10^{5}$ s/eV ($1.2 \times 10^{5}$) s/eV at 68 $\%$ (90 $\%$) CL on the lifetime-to-mass ratio of the mass eigenstates $\nu_2$ and $\nu_1$.
Detecting the end of the cosmic-ray (CR) electron spectrum would provide important new insights. While we know that Milky Way sources can accelerate electrons up to at least $\sim$1PeV, the observed CR electron spectrum at Earth extends only up to 5TeV (possibly 20TeV), a large discrepancy. The question of the end of the CR electron spectrum has received relatively little attention, despite its importance. We take a comprehensive approach, showing that there are multiple steps at which the observed CR electron spectrum could be cut off. At the highest energies, the accelerators may not have sufficient luminosity, or the sources may not allow sufficient escape, or propagation to Earth may not be sufficiently effective, or present detectors may not have sufficient sensitivity. For each step, we calculate a rough range of possibilities. Although all of the inputs are uncertain, a clear vista of exciting opportunities emerges. We outline strategies for progress based on CR electron observations and auxiliary multi-messenger observations. In addition to advancing our understanding of CRs in the Milky Way, progress will also sharpen sensitivity to dark matter annihilation or decay.
We present a series of numerical models suitable for X-ray polarimetry of accreting systems. Firstly, we provide a spectropolarimetric routine that integrates reflection from inner optically thick walls of a geometrical torus of arbitrary size viewed under general inclination. In the studied example, the equatorial torus surrounding an accreting compact object is illuminated by a central isotropic source of X-ray power-law emission, representing a hot corona. Nearly neutral reprocessing inside the walls is precomputed by Monte Carlo code STOKES that incorporates both line and continuum processes, including multiple scatterings and absorption. Applying a conversion script to the torus reflection output, we created tabular dependencies for a new XSPEC model, called xsstokes. In this version, xsstokes enables efficient X-ray polarimetric fitting of the torus parameters, observer's inclination and primary emission properties, interpolating for arbitrary state of primary polarization. We provide comparisons of the results to a more sophisticated Monte Carlo simulation. Since the polarization interpolation routine works for any axially symmetric reflecting structure, we provide another version of xsstokes that is suitable for approximating nearly neutral reflection from a distant optically thick disc of small geometrical thickness. The second version uses the same precomputed Monte Carlo reprocessing, but assumes local illumination averaged for a range of high incident angles, representing a toy model of a diffuse, vertically extended hot inner accretion flow. Assessing both model variants, we conclude that the resulting polarization can be tens of % and perpendicularly/parallelly oriented towards the axis, if the reflecting medium is rather vertically/equatorially distributed.
Among the sample of Galactic transient X-ray binaries (SXTs) discovered to date, about 70 have been proposed as likely candidates to host a black hole. Yet, only 19 have been dynamically confirmed. Such a reliable confirmation requires phase-resolved spectroscopy of their companion stars, which is generally feasible when the system is in a quiescent state. However, since most of the SXT population lies in the galactic plane, which is strongly affected by interstellar extinction, their optical brightness during quiescence usually falls beyond the capabilities of the current instrumentation ($R\gtrsim22$). To overcome these limitations and thereby increase the number of confirmed Galactic black holes, a correlation between the full-width at half maximum (FWHM) of the H$\alpha$ line and the semi-amplitude of the donor's radial velocity curve ($K_2$) was presented in the past. Here, we extend the FWHM-$K_2$ correlation to the near-infrared (NIR), exploiting disc lines such as He I $\lambda$10830, Pa$\gamma$, and Br$\gamma$, in a sample of dynamically confirmed black-hole SXTs. We obtain $K_2 = 0.22(3) ~\textrm{FWHM}$, in good agreement with the optical correlation derived using H$\alpha$. The similarity of the two correlations seems to imply that the widths of H$\alpha$ and the NIR lines are consistent in quiescence. When combined with information on orbital periods, the NIR correlation allows us to constrain the mass of the compact object of systems in quiescence by using single-epoch spectroscopy. We anticipate that this new correlation will give access to highly reddened black-hole SXTs, which cannot be otherwise studied at optical wavelengths.
Be X-ray binaries (Be XRBs) are high-mass X-ray binaries, with a neutron star or black hole orbiting and accreting material from a non-supergiant B-star that is rotating at a near critical rate. These objects are prime targets to understand past binary interactions as the neutron star or black hole progenitor likely experienced Roche lobe overflow to spin up the Be star we observe now. The stellar variability can then allow us to explore the stellar structure of these objects. It was recently demonstrated that the high-mass X-ray binary CPD -29 2176 descended from an ultra-stripped supernova and is a prime target to evolve into an eventual binary neutron star and kilonova. We present the photometric variability from both TESS and ASAS along with the spectral properties and disk variability of the system in this paper. All of the optical lines are contaminated with disk emission except for the He II $\lambda$4686 absorption line. The disk variability time-scales are not the same as the orbital time scale, but could be related to the X-ray outbursts that have been recorded by Swift. We end our study with a discussion comparing CPD -29 2176 to classical Be stars and other Be X-ray binaries, finding the stellar rotation to be near a frequency of 1.5 cycles d$^{-1}$, and exhibiting incoherent variability in three frequency groups.
We introduce the `Resolving supermAssive Black hole Binaries In galacTic hydrodynamical Simulations' (RABBITS) series of studies to investigate the orbital evolution of supermassive black holes (SMBHs) during galaxy mergers. We simulate both disc and elliptical galaxy mergers using the KETJU code, which can simultaneously follow galaxy (hydro-)dynamics and small-scale SMBH dynamics with post-Newtonian corrections. With our SMBH binary subgrid model, we show how active galactic nuclei (AGNs) feedback affects galaxy properties and SMBH coalescence. We find that simulations without AGN feedback exhibit excessive star formation, resulting in merger remnants that deviate from observed properties. Kinetic AGN feedback proves more effective than thermal AGN feedback in expelling gas from the centre and quenching star formation. The different central galaxy properties, which are a result of distinct AGN feedback models, lead to varying rates of SMBH orbital decay. In the dynamical friction phase, galaxies with higher star formation and higher SMBH masses possess denser centres, become more resistant to tidal stripping, experience greater dynamical friction, and consequently form SMBH binaries earlier. As AGN feedback reduces gas densities in the centres, dynamical friction by stars dominates over gas. In the SMBH hardening phase, compared to elliptical mergers, disc mergers exhibit higher central densities of newly formed stars, resulting in accelerated SMBH hardening and shorter merger time-scales (i.e. $\lesssim 500$ Myr versus $\gtrsim 1$ Gyr). Our findings highlight the importance of AGN feedback and its numerical implementation in understanding the SMBH coalescing process, a key focus for low-frequency gravitational wave observatories.
In this second study of the `Resolving supermAssive Black hole Binaries In galacTic hydrodynamical Simulations' (RABBITS) series, we focus on the hardening and coalescing process of supermassive black hole (SMBH) binaries in galaxy mergers. For simulations including different galaxy formation processes (i.e. gas cooling, star formation, SMBH accretion, stellar and AGN feedback), we systematically control the effect of stochastic eccentricity by fixing it to similar values during the SMBH hardening phase. We find a strong correlation between the SMBH merger time-scales and the presence of nuclear star formation. Throughout the galaxy merging process, gas condenses at the centre due to cooling and tidal torques, leading to nuclear star formation. These recently formed stars, which inherit low angular momenta from the gas, contribute to the loss cone and assist in the SMBH hardening via three-body interactions. Compared to non-radiative hydrodynamical runs, the SMBH merger time-scales measured from the runs including cooling, stellar and SMBH physical processes tend to be shortened by a factor of ${\sim}1.7$. After fixing the eccentricity to the range of $e \sim 0.6$--$0.8$ during the hardening phase, the simulations with AGN feedback reveal merger time-scales of ${\sim} 100$--$500$ Myr for disc mergers and ${\sim} 1$--$2$ Gyr for elliptical mergers. With a semi-analytical approach, we find that the torque interaction between the binary and its circumbinary disc has minimal impact on the shrinking of the binary orbit in our retrograde galaxy merger. Our results are useful in improving the modelling of SMBH merger time-scales and gravitational wave event rates.
We propose the use of group convolutional neural network architectures (GCNNs) equivariant to the 2D Euclidean group, $E(2)$, for the task of galaxy morphology classification by utilizing symmetries of the data present in galaxy images as an inductive bias in the architecture. We conduct robustness studies by introducing artificial perturbations via Poisson noise insertion and one-pixel adversarial attacks to simulate the effects of limited observational capabilities. We train, validate, and test GCNNs equivariant to discrete subgroups of $E(2)$ - the cyclic and dihedral groups of order $N$ - on the Galaxy10 DECals dataset and find that GCNNs achieve higher classification accuracy and are consistently more robust than their non-equivariant counterparts, with an architecture equivariant to the group $D_{16}$ achieving a $95.52 \pm 0.18\%$ test-set accuracy. We also find that the model loses $<6\%$ accuracy on a $50\%$-noise dataset and all GCNNs are less susceptible to one-pixel perturbations than an identically constructed CNN. Our code is publicly available at https://github.com/snehjp2/GCNNMorphology.
Active Galactic Nuclei (AGN) in cosmological simulations generate explosive feedback that regulates star formation in massive galaxies, modifying the gas phase structure out to large distances. Here, we explore the direct effects that AGN radiation has on gas heating and cooling within one high-resolution $z=3$ dark matter halo as massive as a quasar host ($M_{\rm h}=$10$^{\rm 12.5}$M$_{\rm\odot}$), run without AGN feedback. We assume AGN radiation to impact the circumgalactic medium (CGM) anisotropically, within a bi-cone of angle $\alpha$. We find that even a relatively weak AGN (black hole mass $M_{\rm\bullet}=10^{\rm 8}$M$_{\rm\odot}$ with an Eddington ratio $\lambda=0.1$) can significantly lower the fraction of halo gas that is catastrophically cooling compared to the case of gas photoionized only by the ultraviolet background (UVB). Varying $M_{\rm\bullet}$, $\lambda$ and $\alpha$, we study their effects on observables. A 10$^{\rm 9}$M$_{\rm\odot}$ AGN with $\lambda=0.1$ and $\alpha\approxeq60^{^{\rm o}}$ reproduces the average surface brightness (SB) profiles of Ly$\alpha$, HeII and CIV, and results in a covering fraction of optically thick absorbers within observational estimates. The simulated SB$_{\rm CIV}$ profile is steeper than observed, indicating that not enough metals are pushed beyond the very inner CGM. For this combination of parameters, the CGM mass catastrophically cooling is reduced by half with respect to the UVB-only case, with roughly same mass out of hydrostatic equilibrium heating up and cooling down, hinting to the importance of self-regulation around AGNs. This study showcases how CGM observations can constrain not only the properties of the CGM itself, but also those of the AGN engine.
The sensitivities of light Dark Matter (DM) particle searches with cryogenic detectors are mostly limited by large backgrounds of events that do not produce ionization signal. The CRYOSEL project develops a new technique where this background in a germanium cryogenic detector is rejected by using the signals from a Superconducting Single Electron Device (SSED) sensor designed to detect the phonons emitted through the Neganov-Trofimov-Luke effect by the e$^-$h$^+$ pairs as they drift in a close-by very high-field region. A tag on signals from this device should suppress the heat-only background. The measurement of the response to IR laser pulses of the first CRYOSEL prototype show the relevance of such sensor technology.
In this study, we analyse the characteristics of stellar populations and the interstellar medium (ISM) in 15,107 early-type central galaxies from the SPIDER survey. Using optical spectra from the Sloan Digital Sky Survey (SDSS), we investigate stellar age (Age), metallicity ($Z$), visual extinction ($A_{\rm V}$), and H$\alpha$ equivalent width (EWH$\alpha$) to understand the evolution of the baryonic content in these galaxies. Our analysis explores the relationship between these properties and central velocity dispersion ($\sigma$) and halo mass ($M_{\rm halo}$) for isolated centrals (ICs) and group centrals (GCs). Our results confirm that both ICs and GCs' stellar populations and gas properties are mainly influenced by $\sigma$, with $M_{\rm halo}$ playing a secondary role. Higher $\sigma$ values correspond to older, more metal-rich stellar populations in both ICs and GCs. Moreover, fixed $\sigma$ values we observe younger Ages at higher values of $M_{\rm halo}$, a consistent trend in both ICs and GCs. Furthermore, we investigate the ionisation source of the warm gas and propose a scenario where the properties of ionised gas are shaped by a combination of cooling within the intra-cluster medium (ICM) and feedback from Active Galactic Nuclei (AGN) assuming a Bondi accretion regime. We observe inherent differences between ICs and GCs, suggesting that the ratio between AGN kinetic power and ICM thermal energy influences EWH$\alpha$ in ICs. Meanwhile, gas deposition in GCs appears to involve a more complex interplay beyond a singular AGN-ICM interaction.
We report the serendipitous discovery of VVV-WIT-12, an unusual variable source that seems to induce variability in its surrounding nebula. The source belongs to the rare objects that we call WITs (short for What Is This?) discovered within the VISTA Variables in the V\'ia L\'actea (VVV) survey. VVV-WIT-12 was discovered during a pilot search for light echoes from distant Supernovae (SNe) in the Milky Way using the near-IR images of the VVV survey. This source has an extremely red spectral energy distribution, consistent with a very reddened ($A_V \sim 100$ mag) long period variable star ($P\sim1525$ days). Furthermore, it is enshrouded in a nebula that changes brightness and color with time, apparently in synch with the central source variations. The near-IR light curve and complementary follow-up spectroscopy observations are consistent with a variable Young Stellar Object (YSO) illuminating its surrounding nebula. In this case the source periodic variation along the cycles produces an unprecedented light echo in the different regions of the nebula.
A complete understanding of the mass assembly history of structures in the universe requires the study of the growth of galaxies and their supermassive black holes (SMBHs) as a function of their local environment over cosmic time. In this context, it is important to quantify the effects that the early stages of galaxy cluster development have on the growth of SMBHs. We used a sample of Herschel/SPIRE sources of $\sim$ 228 red and compact Planck-selected protocluster (PC) candidates to estimate the active galactic nuclei (AGN) fraction from a large sample of galaxies within these candidates. We estimate the AGN fraction by using the mid-infrared (mid-IR) photometry provided by the WISE/AllWISE data of $\sim650$ counterparts at high redshifts. We created an AllWISE mid-IR colour-colour selection using a clustering machine learning algorithm and two {\it WISE} colour cuts using the 3.4 $\mu m$ (W1), 4.6 $\mu m$ (W2) and 12 $\mu m$ (W3) passbands, to classify sources as AGN. We also compare the AGN fraction in PCs with that in the field to better understand the influence of the environment on galaxy development. We found an AGN fraction of $f_{AGN} = 0.113 \pm 0.03$ in PC candidates and an AGN fraction of $f_{AGN} = 0.095 \pm 0.013$ in the field. We also selected a subsample of `red' SPIRE subsample with a higher overdensity significance, obtaining $f_{AGN} = 0.186 \pm 0.044$, versus $f_{AGN} = 0.037 \pm 0.010$ of `non-red sources', consistent with higher AGN fractions for denser environments. We conclude that our results point towards a higher AGN fraction in PCs, similar to other studies.
The peptide-like molecules, cyanoformamide (NCCONH2), is the cyano (CN) derivative of formamide (NH2CHO). It is known to play a role in the synthesis of nucleic acid precursors under prebiotic conditions. In this paper, we present a tentative detection of NCCONH2 in the interstellar medium (ISM) with the Atacama Large Millimeter/submillimeter Array (ALMA) archive data. Ten unblended lines of NCCONH2 were seen around 3sigma noise levels toward Sagittarius B2(N1E), a position that is slightly offset from the continuum peak. The column density of NCCONH2 was estimated to be 2.4\times 10^15 cm ^-2, and the fractional abundance of NCCONH2 toward Sgr B2(N1E) was 6.9\times10^-10. The abundance ratio between NCCONH2 and NH2CHO is estimated to be ~0.01. We also searched for other peptide-like molecules toward Sgr B2(N1E). The abundances of NH2CHO, CH3NCO and CH3NHCHO toward Sgr B2(N1E) were about one tenth of those toward Sgr B2(N1S), while the abundances of CH3CONH2 was only one twentieth of that toward Sgr B2(N1S).
Using the optical spectrum obtained with the Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS) mounted on the Apache Point Observatory (APO) 3.5m Telescope and the Sloan Digital Sky Survey (SDSS) spectrum, we study the properties of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J1046+4047. The galaxy, with a redshift z=0.0487, was selected from the Data Release 16 (DR16) of the SDSS. Its properties are among the most extreme for SFGs in several ways. Its oxygen abundance 12+log(O/H) = 7.091+/-0.016 is among the lowest ever observed. With an absolute magnitude Mg = -16.51 mag, a low stellar mass Mstar = 1.8x10^6 Msun and a very low mass-to-light ratio Mstar/Lg~0.0029 (in solar units), J1046+4047 has a very high specific star-formation rate sSFR~430 Gyr^-1, indicating very active ongoing star formation. Another striking feature of J1046+4047 is that it possesses a ratio O32 = I([OIII]5007)/I([OII]3727) ~57. Using this extremely high O32, we have confirmed and improved the strong-line calibration for the determination of oxygen abundances in the most metal-deficient galaxies, in the range 12+log(O/H) < 7.65. This improved method is appropriate for all galaxies with O32<60 and extends an applicability to highest observed O32 ratios.We find the Halpha emission line in J1046+4047 to be enhanced by some non-recombination processes and thus can not be used for the determination of interstellar extinction.
In this, the third of a series of papers, we present well determined chemical abundances for 124 Planetary nebulae (PNe) in the Galactic bulge from deep, long-slit FORS2 spectra from the 8.2 m ESO Very Large telescope (VLT). Prior to this work there were only ~240 bulge PNe with chemical abundances previously determined over a ~50 year period and of highly variable quality. For 34 of these PNe we are presenting their abundances for the first time which adds ~14% to the available sample of bulge PNe abundances. The interstellar reddening, physical conditions (electron densities, $n_{\mathrm{e}}$, temperatures, $T_{\mathrm{e}}$), and chemical compositions are derived as single values for each PN but also using different line diagnostics. Selected comparisons with the best literature fluxes for 75 PNe in common reveals that these significant new data are robust, reliable and internally self-consistent forming the largest independent, high quality and well understood derivation of PNe abundances currently available for study.
Spiral structure can occupy a significant part of the galaxy, but properly accounting for it in photometric decomposition is rarely done. This may lead to significant errors in the parameters determined. To estimate how exactly neglecting the presence of spiral arms affects the estimation of galaxy decomposition parameters, we perform fitting of 29 galaxies considering spiral arms as a separate component. In this study, we utilize 3.6$\mu$m-band images from the S$^4$G survey and use a new 2D photometric model where each spiral arm is modeled independently. In our model, the light distribution both along and across the arm can be varied significantly, as well as its overall shape. We analyze the differences between models with and without spiral arms, and show that neglecting spiral arms in decomposition causes errors in estimating the parameters of the disk, the bulge, and the bar. We retrieve different parameters of the spiral arms themselves, including their pitch angles, widths, and spiral-to-total luminosity ratio, and examine various relations between them and other galaxy parameters. In particular, we find that the spiral-to-total ratio is higher for galaxies with more luminous discs and with higher bulge-to-total ratios. We report that the pitch angle of spiral arms decreases with increasing bulge or bar fraction. We measure the width of the spiral arms to be 53\% of the disc scale length, on average. We examine the contribution of the spiral arms to the azimuthally-averaged brightness profile and find that spiral arms produce a ``bump'' on this profile with a typical height of 0.3--0.7 mag.
The "chromosome maps" (ChMs) of globular clusters (GCs) have revealed that these ancient structures are not homogeneous in metallicity in various ways, and in different natures. The Type II GCs generally display larger variations, sometimes coupled with slow neutron capture (s) element enrichment on the ChMs redder sequences, which has been interpreted as due to multiple generations of stars. On the other hand, most GCs have inhomogeneous first populations (1P) in the form of large ranges in the Delta(F275W,F814W) values, pointing towards a not fully mixed pristine molecular cloud. We analyse the chemical composition the GC 47 Tucanae, which shows both inhomogeneous 1P stars and, although not formally a Type II GC, hosts a small number of stars distributed on a red side of the main stream of ChM stars. Our results suggest that 1P stars are not homogeneous in the overall metallicity, with variations of the order of ~0.10 dex in all the chemical species. The anomalous stars distributed on a redder sequence of the ChM, are further enriched in metals, but without any evidence for a significant enrichment in the s elements. Our three second population stars located on the normal component of the map, have metallicities similar to those of the metal-richer 1P group, suggesting that this population formed from these stars. Although three stars is a too-small sample to draw strong conclusions, the low spread in metals of these objects might point towards a formation in a fully mixed medium, possibly after a cooling flow phase.
Environmental effects such as ram-pressure stripping (RPS) shape the evolution of galaxies in dense regions. We use the nearby Virgo cluster as a laboratory to study environmental effects on the non-thermal components of star-forming galaxies. We constructed a sample of 17 RPS galaxies in the Virgo cluster and a statistical control sample of 119 nearby galaxies from the Herschel Reference Survey. All objects in these samples are detected in LOFAR 144 MHz observations and come with H$\alpha$ and/or far-UV star formation rate (SFR) estimates. We derived the radio-SFR relations, confirming a clearly super-linear slope of $\approx1.4$. We found that Virgo cluster RPS galaxies have radio luminosities that are a factor of 2-3 larger than galaxies in our control sample. We also investigated the total mass-spectral index relation, where we found a relation for the Virgo cluster RPS galaxies that is shifted to steeper spectral index values by $0.17\pm0.06$. Analyzing the spatially resolved ratio between the observed and the expected radio emission based on the hybrid near-UV + 100$\,\mu$m SFR surface density, we generally observe excess radio emission all across the disk with the exception of a few leading-edge radio-deficient regions. The radio excess and the spectral steepening for the RPS sample could be explained by an increased magnetic field strength if the disk-wide radio enhancement is due to projection effects. For the galaxies that show the strongest radio excesses (NGC 4330, NGC 4396, NGC 4522), a rapid decline of the SFR ($t_\mathrm{quench} \leq 100$ Myr) could be an alternative explanation. We disfavor shock acceleration of electrons as cause for the radio excess since it cannot easily explain the spectral steepening and radio morphology.
Using Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) observations of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J2229+2725, we have discovered an extremely strong nebular CIV 1549, 1551 emission-line doublet, with an equivalent width of 43A, several times higher than the value observed so far in low-redshift SFGs. Together with other extreme characteristics obtained from optical spectroscopy (oxygen abundance 12+log(O/H)=7.085+/-0.031, ratio O32 = I([OIII]5007)/I([OII]3727) ~ 53, and equivalent width of the Hbeta emission line EW(Hbeta) = 577A), this galaxy greatly increases the range of physical properties for dwarf SFGs at low redshift and is a likely analogue of the high-redshift dwarf SFGs responsible for the reionization of the Universe. We find the ionizing radiation in J2229+2725 to be stellar in origin and the high EW(CIV 1549,1551) to be due to both extreme ionization conditions and a high carbon abundance, with a corresponding log C/O = -0.38, that is ~ 0.4 dex higher than the average value for nearby low-metallicity SFGs.
With the launch of JWST, understanding star formation in the early Universe is an active frontier in modern astrophysics. Whether the higher gas pressures and lower metallicities in the early Universe altered the shape of the stellar initial mass function (IMF) remains a fundamental open question. Since the IMF impacts nearly all observable properties of galaxies and controls how stars regulate galaxy growth, determining whether the IMF is variable is crucial for understanding galaxy formation. Here we report the detection of two Lyman-$\alpha$-emitting galaxies in the Epoch of Reionization with exceptionally top-heavy IMFs. Our analysis of JWST/NIRSpec data demonstrates that these galaxies exhibit spectra which are completely dominated by the nebular continuum. In addition to a clear Balmer jump, we observe a steep turnover in the ultraviolet continuum. Although this feature can be reproduced with a contrived damped Lyman-$\alpha$ absorption model, we show instead that this is two-photon emission from neutral hydrogen. Two-photon emission can only dominate if the ionizing emissivity is $\gtrsim10\times$ that of a typical star-forming galaxy. While weak He~{\sc~II} emission disfavours ionizing contributions from AGN or X-ray binaries, such radiation fields can be produced in star clusters dominated by low-metallicity stars of $\gtrsim50\ {\rm M_{\odot}}$, where the IMF is $10-30\times$ more top-heavy than typically assumed. Such a top-heavy IMF implies our understanding of star formation in the early Universe and the sources of reionization may need revision.
Dynamic astrophysical phenomena are predominantly described by differential equations, yet our understanding of these systems is constrained by our incomplete grasp of non-linear physics and scarcity of comprehensive datasets. As such, advancing techniques in solving non-linear inverse problems becomes pivotal to addressing numerous outstanding questions in the field. In particular, modeling hot galactic winds is difficult because of unknown structure for various physical terms, and the lack of \textit{any} kinematic observational data. Additionally, the flow equations contain singularities that lead to numerical instability, making parameter sweeps non-trivial. We leverage differentiable programming, which enables neural networks to be embedded as individual terms within the governing coupled ordinary differential equations (ODEs), and show that this method can adeptly learn hidden physics. We robustly discern the structure of a mass-loading function which captures the physical effects of cloud destruction and entrainment into the hot superwind. Within a supervised learning framework, we formulate our loss function anchored on the astrophysical entropy ($K \propto P/\rho^{5/3}$). Our results demonstrate the efficacy of this approach, even in the absence of kinematic data $v$. We then apply these models to real Chandra X-Ray observations of starburst galaxy M82, providing the first systematic description of mass-loading within the superwind. This work further highlights neural ODEs as a useful discovery tool with mechanistic interpretability in non-linear inverse problems. We make our code public at this GitHub repository (https://github.com/dustindnguyen/2023_NeurIPS_NeuralODEs_M82).
Many disc galaxies host galactic bars, which exert time-dependent, non-axisymmetric forces that can alter the orbits of stars. There should be both angle and radius-dependence in the resulting radial rearrangement of stars ('radial mixing') due to a bar; we present here novel results and trends through analysis of the joint impact of these factors. We use an N-body simulation to investigate the changes in the radial locations of star particles in a disc after a bar forms by quantifying the change in orbital radii in a series of annuli at different times post bar-formation. We find that the bar induces both azimuth angle- and radius- dependent trends in the median distance that stars have travelled to enter a given annulus. Angle-dependent trends are present at all radii we consider, and the radius-dependent trends roughly divide the disc into three 'zones'. In the inner zone, stars generally originated at larger radii and their orbits evolved inwards. Stars in the outer zone likely originated at smaller radii and their orbits evolved outwards. In the intermediate zone, there is no net inwards or outwards evolution of orbits. We adopt a simple toy model of a radius-dependent initial metallicity gradient and discuss recent observational evidence for angle-dependent stellar metallicity variations in the Milky Way in the context of this model. We briefly comment on the possibility of using observed angle-dependent metallicity trends to learn about the initial metallicity gradient(s) and the radial rearrangement that occurred in the disc.
Based on the DECaLS shear catalog, we study the scaling relations between halo mass($M_{\rm h}$) and various proxies for SDSS central galaxies, including stellar mass($M_*$), stellar velocity dispersion($\sigma_*$), abundance matching halo mass($M_{\rm AM}$) and satellite velocity dispersion($\sigma_{\rm s}$), and their dependencies on galaxy and group properties. In general, these proxies all have strong positive correlations with $M_{\rm h}$, consistent with previous studies. We find that the $M_{\rm h}$-$M_*$ and $M_{\rm h}$-$\sigma_*$ relations depend strongly on group richness($N_{\rm sat}$), while the $M_{\rm h}$-$M_{\rm AM}$ and $M_{\rm h}$-$\sigma_{\rm s}$ relations are independent of it. Moreover, the dependence on star formation rate(SFR) is rather weak in the $M_{\rm h}$-$\sigma_*$ and $M_{\rm h}$-$\sigma_{\rm s}$ relations, but very prominent in the other two. $\sigma_{\rm s}$ is thus the best proxy among them, and its scaling relation is in good agreement with hydro-dynamical simulations. However, estimating $\sigma_{\rm s}$ accurately for individual groups/clusters is challenging because of interlopers and the requirement for sufficient satellites. We construct new proxies by combining $M_*$, $\sigma_*$, and $M_{\rm AM}$, and find the proxy with 30\% contribution from $M_{\rm AM}$ and 70\% from $\sigma_*$ can minimize the dependence on $N_{\rm sat}$ and SFR. We obtain the $M_{\rm h}$-supermassive black hole(SMBH) mass relation via the SMBH scaling relation and find indications for rapid and linear growth phases for SMBH. We also find that correlations among $M_{\rm h}$, $M_*$ and $\sigma_*$ change with $M_*$, indicating that different processes drive the growth of galaxies and SMBH at different stages.
Rapid strides are currently being made in the field of artificial intelligence using Transformer-based models like Large Language Models (LLMs). The potential of these methods for creating a single, large, versatile model in astronomy has not yet been explored. In this work, we propose a framework for data-driven astronomy that uses the same core techniques and architecture as used by LLMs. Using a variety of observations and labels of stars as an example, we build a Transformer-based model and train it in a self-supervised manner with cross-survey data sets to perform a variety of inference tasks. In particular, we demonstrate that a $\textit{single}$ model can perform both discriminative and generative tasks even if the model was not trained or fine-tuned to do any specific task. For example, on the discriminative task of deriving stellar parameters from Gaia XP spectra, we achieve an accuracy of 47 K in $T_\mathrm{eff}$, 0.11 dex in $\log{g}$, and 0.07 dex in $[\mathrm{M/H}]$, outperforming an expert $\texttt{XGBoost}$ model in the same setting. But the same model can also generate XP spectra from stellar parameters, inpaint unobserved spectral regions, extract empirical stellar loci, and even determine the interstellar extinction curve. Our framework demonstrates that building and training a $\textit{single}$ foundation model without fine-tuning using data and parameters from multiple surveys to predict unmeasured observations and parameters is well within reach. Such "Large Astronomy Models" trained on large quantities of observational data will play a large role in the analysis of current and future large surveys.
Modelling galaxy formation in hydrodynamic simulations has increasingly adopted various radiative transfer methods to account for photoionization feedback from young massive stars. However, the evolution of HII regions around stars begins in dense star-forming clouds and spans large dynamical ranges in both space and time, posing severe challenges for numerical simulations in terms of both spatial and temporal resolution that depends strongly on gas density ($\propto n^{-1}$). In this work, we perform a series of idealized HII region simulations using the moving-mesh radiation-hydrodynamic code Arepo-RT to study the effects of numerical resolution. The simulated results match the analytical solutions and the ionization feedback converges only if the Str\"omgren sphere is resolved by at least $10$--$100$ resolution elements and the size of each time integration step is smaller than $0.1$ times the recombination timescale. Insufficient spatial resolution leads to reduced ionization fraction but enhanced ionized gas mass and momentum feedback from the HII regions, as well as degrading the multi-phase interstellar medium into a diffuse, partially ionized, warm ($\sim8000$ K) gas. On the other hand, insufficient temporal resolution strongly suppresses the effects of ionizing feedback. This is because longer timesteps are not able to resolve the rapid variation of the thermochemistry properties of the gas cells around massive stars, especially when the photon injection and thermochemistry are performed with different cadences. Finally, we provide novel numerical implementations to overcome the above issues when strict resolution requirements are not achievable in practice.
We present a comprehensive study of the kinematic properties of the different Galactic disk populations, as defined by the chemical abundance ratios and stellar ages, across a large disk volume (4.5 $\leq$ R $\leq$ 15.0 kpc and $|Z|$ $\leq$ 3.0 kpc), by using the LAMOST-Gaia red clump sample stars. We determine the median velocities for various spatial and population bins, finding large-scale bulk motions, such as the wave-like behavior in radial velocity, the north-south discrepancy in azimuthal velocity and the warp signal in vertical velocity, and the amplitudes and spatial-dependences of those bulk motions show significant variations for different mono-age and mono-abundance populations. The global spatial behaviors of the velocity dispersions clearly show a signal of spiral arms and, a signal of the disk perturbation event within 4 Gyr, as well as the disk flaring in the outer region (i.e., $R \ge 12$ kpc) mostly for young or alpha-poor stellar populations. Our detailed measurements of age/[$\alpha$/Fe]-velocity dispersion relations for different disk volumes indicate that young/$\alpha$-poor populations are likely originated from dynamically heated by both giant molecular clouds and spiral arms, while old/$\alpha$-enhanced populations require an obvious contribution from other heating mechanisms such as merger and accretion, or born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium.
Absorbers in the spectrum of background objects probe the circumgalactic medium (CGM) surrounding galaxies, but its physical properties remain unconstrained. We use the cosmological hydrodynamical simulation TNG50 to statistically trace the origins of HI Ly-$\alpha$ absorbers around galaxies at $z = 0.5$ with stellar masses ranging from 10$^8$ to 10$^{11}$ M$_\odot$. We emulate observational CGM studies by considering all gas within a line of sight velocity range of $\pm 500$ km s$^{-1}$ from the central, to quantitatively assess the impact of other galaxy haloes and overdense gas in the IGM that intersect sightlines. The impact of satellites to the total absorber fraction is most significant at impact parameters $0.5 R_{\rm vir} < b < R_{\rm vir}$ and satellites with masses below typical detection limits ($M_* < 10^8$ M$_\odot$) account for 10 (40) per cent of absorbers that intersect any satellite bound to $10^{10}$ and $10^{11}$ $(10^9)$ M$_\odot$ centrals. After confirming outflows are more dominant along the minor axis, we additionally show that at least 20 per cent of absorbers exhibit no significant radial movement, indicating that absorbers can also trace quasi-static gas. The metallicity of absorbers also depends on the azimuthal angle, but this signal is largely driven by enriched inflowing and quasi-static gas. Our work shows that determining the stellar mass of galaxies at $z_{\rm abs}$ is essential to constrain the physical origin of the gas traced in absorption, which in turn is key to characterising the kinematics and distribution of gas and metals in the CGM.
We present numerical characterizations of the wavefront sensing performance for few-mode photonic lantern wavefront sensors (PLWFSs). These characterizations include calculations of throughput, control space, sensor linearity, and an estimate of maximum linear reconstruction range for standard and hybrid lanterns with 3 to 19 ports, at a wavelength of 1550 nm. We additionally consider the impact of beam-shaping optics and a charge-1 vortex mask, placed in the pupil plane. The former is motivated by the application of PLs to high-resolution spectroscopy, which could enable efficient injection into the spectrometer along with simultaneous focal-plane wavefront sensing; similarly, the latter is motivated by the application of PLs to vortex fiber nulling (VFN), which can simultaneously enable wavefront sensing and the nulling of on-axis starlight. Overall, we find that the PLWFS setups tested in this work exhibit good linearity out to ~0.25-0.5 radians of RMS wavefront error (WFE). Meanwhile, we estimate the maximum amount of WFE that can be handled by these sensors, before the sensor response becomes degenerate, to be around ~1-2 radians RMS. In the future, we expect these limits can be pushed further by increasing the number of degrees of freedom, either by adopting higher-mode-count lanterns, dispersing lantern outputs, or separating polarizations. Lastly, we consider optimization strategies for the design of the PLWFS, which involve both modification of the lantern itself and the use of pre- and post-lantern optics like phase masks and interferometric beam recombiners.
Here we present a laboratory analysis of the use of a 19-core photonic lantern (PL) in combination with neural network (NN) algorithms as an efficient focal plane wavefront sensor (FP-WFS) for adaptive optics (AO), measuring wavefront errors such as low wind effect (LWE), Zernike modes and Kolmogorov phase maps. The aberrated wavefronts were experimentally simulated using a Spatial Light Modulator (SLM) with combinations of different phase maps in both the linear regime (average incident RMS wavefront error (WFE) of 0.88 rad) and in the non-linear regime (average incident RMS WFE of 1.5 rad). Results were analysed using a NN to determine the transfer function of the relationship between the incident wavefront error (WFE) at the input modes at the multimode input of the PL and the intensity distribution output at the multicore fibre outputs end of the PL. The root mean square error (RMSE) of the reconstruction of petal and LWE modes were just $2.87\times10^{-2}$ rad and $2.07\times10^{-1}$ rad respectively, in the non-linear regime. The reconstruction RMSE for Zernike combinations ranged from $5.67\times10^{-2}$ rad to $8.43\times10^{-1}$ rad, depending on the number of Zernike terms and incident RMS WFE employed. These results demonstrate the promising potential of PLs as an innovative FP-WFS in conjunction with NNs.
We present a method for precise monitoring of the loop gain of transition edge sensors (TES) under electrothermal feedback. The measurement is implemented on the ICE DfMux electronics and operates simultaneously with Digital Active Nulling (DAN). It uses one additional bias sinusoid per TES and does not require any additional readout channels. The loop gain monitor is being implemented on the Simons Array and is an integral part of the baseline calibration strategy for the upcoming LiteBIRD satellite.
The empirical law of Gladstone-Dale is insufficient for high-precision studies using the refractivity of a gas: this is not exactly proportional to its density, and the gas may not be properly described as perfect. An optical Mariotte temperature allows making a comparative analysis of the results given by various authors. The effect of hygrometry on the refractivity at visible wavelengths is historically traced and its small effect on the astronomical refraction angle numerically shown. Finally at infrared and radio wavelengths, the effects of the humidity in the lower atmosphere can be strong; as for the ionosphere, its curvature plays an essential role for the astronomical refraction angle unlike in the visible.
The fundamental quadrature governing light rays in a spherically symmetrical medium is first recalled. A rigorous discussion of some qualitative properties of its solutions follows, using the Young-Kattawar diagram which leads to a geometric formulation of the ray curvature. The case of an optical duct is deepened, analyzing transfer curves for different positions of the observer with respect to the duct. New analytical expressions for their wavelength dependence are derived, and their numerical consequences are coherent with computer simulations.
We present a model for the transport of anisotropic turbulence in an accretion disc. The model uses the Reynolds stress tensor approach in the mean field approximation. To study the role of convection in a protoplanetary disc, we combine the turbulence model with a radiative transfer calculation, and also include convection using the mixing length approximation. We find that the turbulence generated by convection causes the angular momentum of the accretion disc to be directed outwards. We also confirm the conclusions of other authors that turbulent convection is unable to provide the observed disc accretion rates as well as a heat source sufficient for the convection to be self-sustaining. The reasons for the latter are the strong anisotropy of the turbulence together with the low efficiency of the energy transfer from the background velocity shear to the turbulent stress tensor.
This paper delves into the exploration of suitable boundary conditions for the asymptotically flat scenario of general relativity presented in terms of Ashtekar-Barbero variables. While the standard parity conditions have been extensively studied in \cite{Thiemann, Campiglia}, it turns out that they fail to produce non-trivial supertranslations at spatial infinity. We propose new parity conditions for the Ashtekar-Barbero variables that do yield non-trivial supertranslation charges at spatial infinity. We compare our findings with those presented in \cite{Henneaux} and demonstrate that the new boundary conditions ensure the finiteness of the symplectic structure. Moreover, when embarking on the quest for appropriate parity conditions, it is essential to ensure that the selected parities remain invariant under hypersurface deformations. Given that working with Ashtekar-Barbero variables provides more asymptotic structure as compared to the ADM variables, it is shown that by fixing the Lagrange multiplier corresponding to the Gauss constraint, the invariance of certain parity conditions can be guaranteed.
Considering an arbitrary dimensional FLRW universe in the framework of a generalized S\'{a}ez--Ballester (SB) theory, we establish a noncommutative (NC) cosmological model. We concentrate on the predictions of NC model and compare them with their commutative counterparts in both the classical and quantum regimes. For the classic case, taking a very small NC parameter, we apply two different methods to analyze the model features. First, we show through numerical analysis that our NC model is a successful inflationary model capable of overcoming the graceful exit and horizon problems. Furthermore, the NC traces are visible the late time, which supports the UV/IR mixing characteristic of the NC models. In the second method, we show that our NC model can correspond to the previously developed NC inflationary models. In the commutative quantum case, we obtain an exact wave function and then use the WKB approximation to show that the solutions of the corresponding classical regime are recovered. Finally, with regard to the NC quantum level, we focus on the special case for which we show that a constant of motion exists. The latter helps us to conveniently transform the corresponding complicated NC-WDW equation into an ordinary differential equation, which can be easily solved numerically for the general case or analytically for some special cases. The resultant solutions show a damping behavior in the wave function associated with the proposed NC model, which may be important in determining the viable initial states for the very early universe.
We examined the quantum properties of scalar-tensor gravity with a coupling to the Gauss-Bonnet term, exploring both linear and quadratic couplings. We calculate the leading order corrections to the non-relativistic one-body gravitational potential and the metric studying the external gravitational field of a point-like scalar particle. The light-like scattering was studied and compared with the classical theory. We find that loop corrections are strongly suppressed and cannot significantly affect the black hole shadow for quadratic coupling. The leading order corrections are important for small-angle scattering and can contribute to the formation of the black hole shadow for the case of linear coupling.
Dipole charge conservation forces isolated charges to be immobile fractons. These couple naturally to spatial two-index symmetric tensor gauge fields that resemble a spatial metric. We propose a spacetime Lorentz covariant version of dipole symmetry and study the theory of the associated gauge fields. In the presence of a suitable background field, these contain a massive anti-symmetric and a massless symmetric two-index tensors. The latter transforms only under longitudinal diffeomorphisms, making the massless sector similar to linearized gravity, but with additional modes of lower spin. We show that the theory can be consistently coupled to a curved background metric and study its possible interaction terms with itself and with matter. In addition, we construct a map between solutions of linearized gravity in Kerr-Schild form and solutions of fracton gravity coupled to matter.
Null cosmic strings are shown to disturb gravitational fields of massive bodies and create outgoing gravitational waves (GW). Perturbations of the metric caused by a straight null string and a point-like massive source are found as solutions to linearized Einstein equations on a flat space-time. An analytic approximation for their asymptotic at future null infinity is derived. A space-time created by the source and the string is shown to have asymptotically polyhomogeneous form. We calculate GW flux in such space-times and demonstrate that the averaged intensity of the radiation is maximal in the direction of the string motion. Opportunities to detect null string generated gravity waves are briefly discussed.
We explore a cosmological model inspired by the modified Kaniadakis entropy and disclose the influences of the modified Friedmann equations on the evolution of the Universe. We find that in modified Kaniadakis cosmology with only pressure-less matter, one can reproduce the accelerated Universe without invoking any kind of dark energy. We delved into the evolution of the Universe during the radiation-dominated era as well. We also investigate the behavior of the scale factor and the deceleration parameter for a multiple-component Universe consisting of pressure-less matter and a cosmological constant/dark energy. Interestingly enough, the predicted age of the Universe in the modified Kaniadakis cosmology becomes larger compared to the standard cosmology which may alleviate the age problem. Furthermore, The findings reveal that in the modified Kaniadakis cosmology, the transition from a decelerated phase to an accelerated Universe occurs at higher redshifts compared to the standard cosmology. These results shed light on the potential implications of incorporating Kaniadakis entropy into cosmological models and provide valuable insights into the behavior of the Universe in different cosmological scenarios. Moreover, they emphasize the crucial role of modifications to the geometry component and the significance of such modifications in understanding the dynamics of the Universe.
An interesting idea, dating back to Feynman, argues that quantum mechanics may break down for large masses if one entertains the possibility that gravity can be "classical", thereby leading to predictions different from conventional low-energy quantum gravity. Despite the technical difficulty in testing such deviations, a large number of experimental proposals have been put forward due to the high level of fundamental interest. Here, we consider the Schr\"odinger-Newton (SN) theory and the Correlated Worldline (CWL) theory, and show that they can be distinguished from conventional quantum mechanics, as well as each other, by performing pulsed optomechanics experiments. For CWL specifically we develop a framework resembling the commonly used "Heisenberg-picture" treatment of coupled oscillators, allowing one to perform simple calculations for such systems without delving into the deeper path-integral formalism. We find that discriminating between the theories will be very difficult until experimental control over low frequency quantum optomechanical systems is pushed much further. However, the predicted departures of SN and CWL from quantum mechanics occur at the same scale, so both alternative models could in principle be probed by a single experiment.
We obtain a \textit{novel} model of oscillating non-singular cosmology on the spatially flat Randall-Sundrum (RS) II brane. At early times, the universe is dominated by a scalar field with an inflationary emergent potential $V(\phi)=A(e^{B\phi}-1)^2$, $A$ and $B$ being constants. Interestingly, we find that such a scalar field can source a non-singular bounce, replacing the big bang on the brane. The turnaround again happens naturally on the brane dominated by a phantom dark energy (favoured by observations\cite{E1,E2,E3} at late times), thus avoiding the big rip singularity and leading upto the following non-singular bounce via a contraction phase. There is a smooth non-singular transition of the brane universe through both the bounce and turnaround, leading to alternate expanding and contracting phases. This is the \textit{first} model where a single braneworld of positive tension can be made to recycle as discussed in details in the concluding section.
We consider an initial data set having a continuous symmetry and a marginally outer trapped surface (MOTS) that is not preserved by this symmetry. We show that such a MOTS is unstable except in an exceptional case. In non-rotating cases we provide a Courant-type lower bound on the number of unstable eigenvalues. These results are then used to prove the instability of a large class of exotic MOTS that were recently observed in the Schwarzschild spacetime. We also discuss the implications for the apparent horizon in data sets with translational symmetry.
We construct an infinite family of microstates for black holes in Minkowski spacetime which have effective semiclassical descriptions in terms of collapsing dust shells in the black hole interior. Quantum mechanical wormholes cause these states to have exponentially small, but universal, overlaps. We show that these overlaps imply that the microstates span a Hilbert space of log dimension equal to the event horizon area divided by four times the Newton constant, explaining the statistical origin of the Bekenstein-Hawking entropy.
In a recent paper, with Drago and Pinamonti we have introduced a Wetterich-type flow equation for scalar fields on Lorentzian manifolds, using the algebraic approach to perturbative QFT. The equation governs the flow of the effective average action, under changes of a mass parameter k. Here we introduce an analogous flow equation for gauge theories, with the aid of the Batalin-Vilkovisky (BV) formalism. We also show that the corresponding effective average action satisfies a Slavnov-Taylor identity in Zinn-Justin form. We interpret the equation as a cohomological constraint on the functional form of the effective average action, and we show that it is consistent with the flow.
We study the geodesic motion of uncharged particles in the background of a magnetically charged Euler-Heisenberg black hole with a scalar hair. The spacetime can be asymptotically (A)dS or flat and we find, analysing the behavior of the effective potential of the radial motion that in all cases there exist stable and unstable orbits. Performing numerical integrations we depict the motion of particles for planetary and critical orbits, as well as for radial geodesics. We discuss the effect that the scalar hair $\nu$, the magnetic charge $Q_{m}$ and the Euler-Heisenberg parameter $\alpha$ have on the particle motion.
We investigate thermodynamic schemes of charged BTZ-like black holes in arbitrary dimensions, namely higher-dimensional charged black holes in which the electromagnetic sector exhibits the same properties with that of the usual three-dimensional BTZ solution. We first present the Euclidean on-shell action in arbitrary dimensions, inserting a radial cutoff. We then extract the corresponding thermodynamic quantities from the semi-classical partition function in different ensembles and find that there exist two possible thermodynamic schemes, with different outcomes. Regarding the traditional scheme (scheme I), where the length cutoff is identified with the AdS radius, we show that charged BTZ-like black holes are super-entropic, namely they violate the reverse isoperimetric inequality conjecture, and their super-entropicity is strongly connected to a fundamental thermodynamic instability. This class of solutions is the first demonstration of super-entropic black holes which possess second-order critical points and, since thermodynamic instabilities always arise, it is not possible to physically interpret the corresponding van der Waals critical phenomenon in this scheme. In the second scheme (II) where the length cutoff is considered as an independent variable, namely the system respects the conjectured reverse isoperimetric inequality, we show that the solutions are thermodynamically stable in an ensemble where the length cutoff is kept fixed, and hence one can provide an explanation for the van der Waals critical phenomenon. Furthermore, in order to verify the consistency of the second scheme, we study the Joule-Thomson expansion and we extract the Joule-Thomson coefficient, the inversion temperature, the inversion curves, and the isenthalpic curves. The results indicate that this class of AdS black holes can be considered as interacting statistical systems. Additionally, ...
We introduce a theoretical framework to interpret the Hubble tension, based on the combination of a metric $f(R)$ gravity with a dynamical dark energy contribution. The modified gravity provides the non-minimally coupled scalar field responsible for the proper scaling of the Hubble constant, in order to accommodate for the local SNIa pantheon+ data and Planck measurements. The dynamical dark energy source, which exhibits a phantom divide line separating the low red-shift quintessence regime ($-1<w<-1/3$) from the phantom contribution ($w<-1$) in the early Universe, guarantees the absence of tachyonic instabilities at low red-shift. The resulting $H_0(z)$ profile rapidly approaches the Planck value, with a plateau behaviour for $z\gtrsim 5$. In this scenario, the Hubble tension emerges as a low red-shift effect, which can be in principle tested by comparing SNIa predictions with far sources, like QUASARS and Gamma Ray Bursts.
Despite the absence of a lightcone structure, some solutions of Carroll gravity show black hole-like behaviour. We define Carroll black holes as solutions of Carroll gravity that exhibit Carroll thermal properties and have a Carroll extremal surface, notions introduced in our work. The latter is a Carroll analogue of a Lorentzian extremal surface. As examples, we discuss the Carroll versions of Schwarzschild, Reissner-Nordstroem, and BTZ black holes and black hole solutions of generic 1+1 dimensional Carroll dilaton gravity, including Carroll JT and Carroll Witten black holes.
We present a brief overview of fractional analytic QCD.
Tetraquarks, bound states composed of two quarks and two antiquarks, have been the subject of intense study but have yet to be understood from first principles. Previous studies of fully-heavy tetraquarks in nonrelativistic effective field theories of quantum chromodynamics (QCD) suggest different conclusions for their existence. We apply variational and Green's function Monte Carlo methods to compute tetraquarks' ground- and excited-state energies in potential nonrelativistic QCD. We robustly demonstrate that fully-heavy tetraquarks are bound in QCD for sufficiently heavy quark masses. We also predict the masses of tetraquark bound states comprised of $b$ and $c$ quarks, which are experimentally accessible, and suggest possible resolutions for previous theoretical discrepancies.
We derive a set of sum rules needed for KK-graviton scattering and KK-graviton pair production from matter in orbifolded extra-dimensional models. The sum rules can be found in full generality by considering the properties of solutions to the Sturm-Liouville problem, which describes the wave functions and the masses of the KK-gravitons in four dimensions. They ensure cancellations in the amplitudes of the processes mentioned above which considerably reduce their growth with $s$ in the high-energy limit. This protects extra-dimensional theories from the low-scale unitarity problems that plague other theories with massive spin-2 particles. We argue that such relations are valid for a broader category of models.
We present the first study of the quark mass dependence of the heavy quark momentum and spatial diffusion coefficients using lattice QCD with light dynamical quarks corresponding to a pion mass of 320 MeV. We find that, for the temperature range 195 MeV $<T<$ 293 MeV, the spatial diffusion coefficients of the charm and bottom quarks are smaller than those obtained in phenomenological models that describe the $p_T$ spectra and elliptic flow of open heavy flavor hadrons.
In pursuit of precise and fast theory predictions for the LHC, we present an implementation of the MadNIS method in the MadGraph event generator. A series of improvements in MadNIS further enhance its efficiency and speed. We validate this implementation for realistic partonic processes and find significant gains from using modern machine learning in event generators.
Model-independent theoretical upper bound on the thermal dark matter (DM) mass can be derived from the maximum inelastic DM cross-section featuring the whole observed DM abundance. We deploy partial-wave unitarity of the scattering matrix to derive the maximal thermally-averaged cross section for general number-changing processes $r\to 2$ (with $r\ge 2$), which may involve standard model particles or occur solely within the dark sector. The usual upper limit on the DM mass for s-wave annihilation is around 130TeV (1GeV) for $r=2$ (3), only applies in the case of a freeze out occurring in the standard cosmological scenario. We consider the effects of two nonstandard cosmological evolutions, characterized by low-temperature reheating: $i)$ a kination-like scenario and $ii)$ an early matter dominated scenario. In the first case, the early freeze-out strengthens the unitarity bound to few TeVs for WIMPs; while in the second case, WIMP DM can be as heavy as $\sim 10^{10}$GeV due to a large entropy dilution.
Exploiting crossing symmetry, the hadron scale pion valence quark distribution function is used to predict the kindred elementary valence quark fragmentation function (FF). This function defines the kernel of a quark jet fragmentation equation, which is solved to obtain the full pion FFs. After evolution to a scale typical of FF fits to data, the results for quark FFs are seen to compare favourably with such fits. However, the gluon FF is markedly different. Notably, although FF evolution equations do not themselves guarantee momentum conservation, inclusion of a gluon FF which, for four quark flavours, distributes roughly 11% of the total light-front momentum fraction, is sufficient to restore momentum conservation under evolution. Overall, significant uncertainty is attached to FFs determined via fits to data; hence, the features of the predictions described herein could potentially provide useful guidance for future such studies.
We propose the first practical method to detect atmospheric tau neutrino appearance at sub-GeV energies, which would be an important test of $\nu_\mu \rightarrow \nu_\tau$ oscillations and of new-physics scenarios. In the Jiangmen Underground Neutrino Observatory (JUNO; starts in 2024), active-flavor neutrinos eject neutrons from carbon via neutral-current quasielastic scattering. This produces a two-part signal: the prompt part is caused by the scattering of the neutron in the scintillator, and the delayed part by its radiative capture. Such events have been observed in KamLAND, but only in small numbers and were treated as a background. With $\nu_\mu \rightarrow \nu_\tau$ oscillations, JUNO should measure a clean sample of 55 events/yr; with simple $\nu_\mu$ disappearance, this would instead be 41 events/yr, where the latter is determined from Super-Kamiokande charged-current measurements at similar neutrino energies. Implementing this method will require precise laboratory measurements of neutrino-nucleus cross sections or other developments. With those, JUNO will have $5\sigma$ sensitivity to tau-neutrino appearance in 5 years exposure, and likely sooner.
Large linear systems play an important role in high-energy theory, appearing in amplitude bootstraps and during integral reduction. This paper introduces FiniteFieldSolve, a general-purpose toolkit for exactly solving large linear systems over the rationals. The solver interfaces directly with Mathematica, is straightforward to install, and seamlessly replaces Mathematica's native solvers. In testing, FiniteFieldSolve is approximately two orders of magnitude faster than Mathematica and uses an order of magnitude less memory. The package also compares favorably against other public solvers in FiniteFieldSolve's intended use cases. As the name of the package suggests, solutions are obtained via well-known finite field methods. These methods suffer from introducing an inordinate number of modulo (or integer division) operations with respect to different primes. By automatically recompiling itself for each prime, FiniteFieldSolve converts the division operations into much faster combinations of instructions, dramatically improving performance. The technique of compiling the prime can be applied to any finite field solver, where the time savings will be solver dependent. The operation of the package is illustrated through a detailed example of an amplitude bootstrap.
The possibility of searching for right-handed neutrinos at the MoEDAL's Apparatus for Penetrating Particles (MAPP) detector is investigated in this work. In particular, pair-production of right-handed (RH) neutrinos $N$ from either a $B-L$ gauge boson $Z'$, as well as Standard Model (SM) $Z$ boson are considered. Under a no-background assumption, we show that the MAPP detector can be sensitive to active-sterile neutrino mixing strengths as low as $V_{\mu N}^2 \approx 10^{-12}$ for multiple choices of $m_N / m_{Z'}$ values, when taking the $B-L$ gauge coupling $g_{B-L} = 10^{-3}$ near its current limit. The SM $Z$ boson portal can reach a similar sensitivity, when the effective mixing between the $B-L$ and SM gauge boson is $\alpha \approx 0.01$.
A sample of 3984 candidates of the $K^+\to\pi^+\gamma\gamma$ decay, with an estimated background of $291\pm14$ events, was collected by the NA62 experiment at CERN during 2017-2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be $(9.61\pm0.17)\times10^{-7}$. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^+\to\pi^+a$, $a\to\gamma\gamma$ is also reported.
We discuss the combination of NLO QCD corrections with operators of canonical dimension six within Standard Model Effective Field Theory (SMEFT), as well as within non-linear Effective Field Theory (HEFT) for Higgs-boson pair production in gluon fusion. Particular emphasis will be put on the identification of leading and subleading operators contributing to this process.
Results for the full electroweak two-loop contributions of O(Nc^2), where Nc is the colour factor, to the Higgs-boson masses in the MSSM are obtained using a Feynman-diagrammatic approach including the full dependence on the external momentum. These corrections are expected to constitute the dominant part of the two-loop corrections that were still missing up to now. As a consequence of working at O(Nc^2), the relevant two-loop self-energies decompose into products of one-loop integrals, giving rise to a transparent analytical structure of the self-energies. We compare different renormalisation schemes for tanb, the ratio of the vacuum expectation values of the two Higgs doublets, and demonstrate under which conditions different renormalisation schemes can be related to each other via a simple reparametrisation. We explicitly show that this is in general not possible for mixed renormalisation schemes due to the presence of evanescent terms. In our numerical analysis, the new corrections are compared with already known two-loop contributions and the experimental uncertainty of the mass of the observed Higgs boson. While smaller than the already known two-loop corrections, the new terms are typically larger in size than the experimental uncertainty. This underlines the relevance of the so-far unknown electroweak two-loop contributions.
We calculate the pion scattering amplitude at nonzero temperature and nonzero $\mu_5$, the chemical potential associated to chiral imbalance in a locally $P$-breaking scenario. The amplitude is calculated up to next to leading order in Chiral Perturbation Theory and is unitarized with the Inverse Amplitude Method to generate the poles of the $f_0(500)$ and $\rho (770)$ resonances. Within the saturation approach, the thermal $f_0(500)$ pole allows to determine $T_c(\mu_5)$, the transition temperature for chiral symmetry restoration. Our results confirm the growing behaviour of $T_c(\mu_5)$ found in previous works and, through a fit to lattice results, we improve the uncertainty range of the low-energy constants associated to $\mu_5$ corrections in the chiral lagrangian. The results for the $\rho (770)$ pole are compatible with previous works regarding the dilepton yield in heavy-ion collisions.
Strong motivation for investing in quantum sensing arises from the need to investigate phenomena that are very weakly coupled to the matter and fields well described by the Standard Model. These can be related to the problems of dark matter, dark sectors not necessarily related to dark matter (for example sterile neutrinos), dark energy and gravity, fundamental constants, and problems with the Standard Model itself including the Strong CP problem in QCD. Resulting experimental needs typically involve the measurement of very low energy impulses or low power periodic signals that are normally buried under large backgrounds. This report documents the findings of the 2023 Quantum Sensors for High Energy Physics workshop which identified enabling quantum information science technologies that could be utilized in future particle physics experiments, targeting high energy physics science goals.
The mediator particle between the Standard Model sector and a hidden sector might have a long lifetime to show the observable displaced vertices in experiments. Considering a fermionic dark matter model in which the hidden sector is connected to the Standard Model by an additional Higgs doublet field, the mediator dark $Z$ boson may live long enough. We explore the possibility to observe the displaced vertices of the long-lived dark $Z$ boson at the CERN LHC and at the proposed SHiP experiment. We find that the ATLAS and CMS searches for the long-lived dark $Z$ boson can probe the mass range $7 < m_{Z'} < 150~{\rm MeV}$ with 150 fb$^{-1}$ integrated luminosity at the LHC run 3, and the SHiP experiment will probe $2 m_e < m_{Z'} < 15~{\rm MeV}$ range with $6 \times 10^{20}$ protons on target in total 15 years. The dark matter phenomenology is also discussed in the region where such a long-lived mediator is detectable.
We investigate possible signatures of gluon saturation using forward $p+A \to j+j+X$ di-jet production processes at the Large Hadron Collider. In the forward rapidity region, this is a highly asymmetric process where partons with large longitudinal momentum fraction \(x\) in the dilute projectile are used as a probe to resolve the small \(x\) partonic content of the dense target. Such dilute-dense processes can be described in the factorization framework of Improved Transverse Momentum Distributions (ITMDs). We present a new model for ITMDs where we explicitly introduce the impact parameter (\(b\)) dependence in the ITMDs, to properly account for the nuclear enhancement of gluon saturation effects, and discuss the phenomenological consequences for $p-Pb$, $p-Xe$ and $p-O$ collisions at the LHC. While the case of $p-p$ and $e-p$ collisions is used to fix the model parameters, we find that, on average, the nuclear enhancement of the saturation scale is noticeably weaker than expected from naive scaling with a simple dependence on the atomic number. Since our model explicitly accounts for event-by-event fluctuations of the nuclear geometry, it can also be applied to study forward central correlations in $p-A$ collisions.
We conduct an investigation on the $1P$- and $2P$-wave charmed baryons using the methods of QCD sum rules and light-cone sum rules within the framework of heavy quark effective theory. Our results suggest that the $\Lambda_c(2910)^+$, $\Lambda_c(2940)^+$, and $\Xi_c(3123)^+$ can be well interpreted as the $2P$-wave charmed baryons of $J^P=1/2^-$ and $3/2^-$, belonging to the $SU(3)$ flavor $\mathbf{\bar 3}_F$ representation. Moreover, the $\Xi_c(3123)^+$ possesses a partner state characterized by $J^P=1/2^-$, denoted as $\Xi_c(1/2^-,2P)$. Our analysis predicts its mass and width to be $m_{\Xi_c(1/2^-,2P)} - m_{\Xi_c(3123)^+} = -18\pm{7}$MeV and $\Gamma_{\Xi_c(2P,1/2^-)}=31^{+170}_{-27}$MeV, with $m_{\Xi_c(3123)^+} = 3122.9\pm{1.3}$MeV. We propose to search for it in the $\Xi_c(1/2^-,2P)\to \Sigma_c K$ decay channel.
The $\Xi N$ interaction plays an important role in our understanding on the long-anticipated $H$-dibaryon. Recent lattice QCD calculations verified the attractive nature of the $\Xi N$ interaction. On the other hand, whether it is strong enough to generate a bound state remains inconclusive.In this work, assuming that it can generate a weakly bound state, we study the yields of the $\Xi N$ dibaryon for different binding energies in $pp$ collisions at 7 TeV using the coalescence model and the transport model PACIAE. The yields are estimated first numerically and then analytically adopting a Yukawa-type wave function. In particular, we find that in the weak binding limit, there exists a universal relation between the yield and the binding energy, valid for $pp$ collisions.
In this talk, we present the program Lilith, a python package for constraining new physics from Higgs measurements. We discuss the usage of signal strength results in the latest published version of Lilith, which allows for constraining deviations from SM Higgs couplings through coupling modifiers. Moreover, we discuss the on-going development to include Higgs STXS data and SMEFT parametrizations in Lilith with the aim of performing global fits of the ATLAS and CMS data. As we point out, detailed information on Standard Model uncertainties and their correlations is important to enable the proper reuse of the experimental results.
Correlations involving the seven conserved quantities, namely energy, baryon number, electric charge, strangeness, and the three components of momentum, give rise to correlations in heavy-ion collisions. Through the utilization of a simple one-dimensional hydrodynamic model, we calculate the evolution of the entire $7\times7$ matrix of correlations as a function of relative spatial rapidity. This comprehensive analysis accounts for finite baryon density, which results in off-diagonal correlations between the charge-related quantities and the energy-momentum quantities. These correlations in coordinate space are subsequently transformed into correlations in momentum space using statistical weighting. The entire matrix of correlations is revealed to be highly sensitive to the equation of state (EoS), viscosity, and diffusivity.
We study how vacuum neutrino oscillations can be affected by a causal, nonlinear and state-dependent modification of quantum field theory that may be interpreted using the many-worlds formulation of quantum mechanics. The effect is induced by a Higgs-neutrino Yukawa interaction that causes a nonlinear interference between the neutrino mass eigenstates. This leads to a tiny change in the oscillation pattern of light, active neutrinos without altering the oscillation frequencies. At large baselines where the oscillations disappear, the nonlinear effect is also suppressed and does not source correlations between the mass eigenstates once they are entangled with the environment. Our example provides a way to compute effects of nonlinear quantum mechanics and field theory that may probe the possible physical reality of many worlds.
We provide a formulation of potential non-relativistic quantum chromodynamics (pNRQCD) suitable for calculating binding energies and matrix elements of generic hadron and multi-hadron states made of heavy quarks in $SU(N_c)$ gauge theory using quantum Monte Carlo techniques. We compute masses of quarkonium and triply-heavy baryons in order to study the perturbative convergence of pNRQCD and validate our numerical methods. Further, we study $SU(N_c)$ models of composite dark matter and provide simple power series fits to our pNRQCD results that can be used to relate dark meson and baryon masses to the fundamental parameters of these models. For many systems comprised entirely of heavy quarks, the quantum Monte Carlo methods employed here are less computationally demanding than lattice field theory methods, although they introduce additional perturbative approximations. The formalism presented here may therefore be particularly useful for predicting composite dark matter properties for a wide range of $N_c$ and heavy fermion masses.
A large amount of data on hadronic two body weak decays of anti-triplet charmed baryons $T_{c\bar 3}$ to an octet baryon $T_8$ and an octet or singlet pseudoscalar meson $P$, $T_{c \bar 3} \to T_8 P$, have been measured. The SU(3) flavor symmetry has been applied to study these decays to obtain insights about weak interactions for charm physics. However not all such decays needed to determine the SU(3) irreducible amplitudes have been measured forbidding a complete global analysis. Previously, it has been shown that data from measured decays can be used to do a global fit to determine all except one parity violating and one parity conserving amplitudes of the relevant SU(3) irreducible amplitudes causing 8 hadronic two body weak decay channels involving $\Xi^0_c$ to $\eta$ or $\eta'$ transitions undetermined. It is important to obtain information about these decays in order to guide experimental searches. In this work using newly measured decay modes by BESIII and Belle in 2022, we carry out a global analysis and parameterize the unknown amplitudes to provide the ranges for the branching ratios of the 8 undetermined decays. Our results indicate that the SU(3) flavor symmetry can explain the measured data exceptionally well, with a remarkable minimal $\chi^2/d.o.f.$ of 1.21 and predict 80 observables in 45 decays for future experimental data to test. We then vary the unknown SU(3) amplitudes to obtain the allowed range of branching ratios for the 8 undetermined decays. We find that some of them are within reach of near future experimental capabilities. We urge our experimental colleagues to carry out related searches.
In nuclear collisions at RHIC energies, an excess of $\Omega$ hyperons over $\bar{\Omega}$ is observed, indicating that $\Omega$ carries a net baryon number despite $s$ and $\bar{s}$ quarks being produced in pairs. The baryon number in $\Omega$ could have been transported from the incident nuclei and/or produced in baryon-pair production of $\Omega$ with other types of anti-hyperons, such as $\bar{\Xi}$. To investigate these two scenarios, we propose to measure correlations between $\Omega$ and $K$, as well as between $\Omega$ and anti-hyperons. We will use two versions, the default and string-melting, of a multiphase transport (AMPT) model to illustrate the method to measure the correlation and to demonstrate the general shape of the correlation. We will present the $\Omega$-hadron correlations from simulated $\mathrm{Au}$+$\mathrm{Au}$ collisions at $\sqrt{s_{NN}} = 7.7$ and $14.6 \ \mathrm{GeV}$, and discuss the dependence on collision energy and on the hadronization scheme in these two AMPT versions. These correlations can be used to explore the mechanism of baryon number transport and the effects of baryon number and strangeness conservation in nuclear collisions.
The computational cost associated with reducing tensor integrals to scalar integrals using the Passarino-Veltman method is dominated by the diagonalisation of large systems of equations. These systems of equations are sized according to the number of independent tensor elements that can be constructed using the metric and external momenta. In this article, we present a closed-form solution of this diagonalisation problem in arbitrary tensor integrals. We employ a basis of tensors whose building blocks are the external momentum vectors and a metric tensor transverse to the space of external momenta. The scalar integral coefficients of the basis tensors are obtained by mapping the basis elements to the elements of an orthogonaldual basis. This mapping is succinctly expressed through a formula that resembles the ordering of operators in Wick's theorem. Finally, we provide examples demonstrating the application of our tensor reduction formula to Feynman diagrams in QCD $2 \to 2$ scattering processes, specifically up to three loops.
In this study, we determine the mass radius of $^4$He, a very light nucleus, by examining the near-threshold $\phi$-meson photoproduction data of the LEPS Collaboration. To assess the gravitational form factor of $^4$He, we employ multiple models for the mass distribution, including Yukawa-type, exponential, Gaussian, and uniform functions. The mass radius of $^4$He is measured to be $1.70\pm0.14$ fm, which is approximately equal to the charge radius of $^4$He. Surprisingly, in contrast to the findings of the proton, no noticeable discrepancy between the charge radius and the mass radius is noted for the $^4$He nucleus. The proton and neutron distributions within $^4$He are likely to be identical, confirming its regular tetrahedral structure in a new way. We propose exploring the difference between charge and mass radii as a new approach to examine the nuclear structure.
We explore the efficacy of entanglement entropy as a tool for detecting thermal phase transitions in a family of gauge theories described holographically. The rich phase diagram of these theories encompasses first and second-order phase transitions, as well as a critical and a triple point. While entanglement measures demonstrate some success in probing transitions between plasma phases, they prove inadequate when applied to phase transitions leading to gapped phases. Nonetheless, entanglement measures excel in accurately determining the critical exponent associated with the observed phase transitions, providing valuable insight into the critical behavior of these systems.
In this talk we review jet production in a large variety of collision systems using the JETSCAPE event generator and Hybrid Hadronization. Hybrid Hadronization combines quark recombination, applicable when distances between partons in phase space are small, and string fragmentation appropriate for dilute parton systems. It can therefore smoothly describe the transition from very dilute parton systems like $e^++e^-$ to full $A+A$ collisions. We test this picture by using JETSCAPE to generate jets in various systems. Comparison to experimental data in $e^++e^-$ and $p+p$ collisions allows for a precise tuning of vacuum baseline parameters in JETSCAPE and Hybrid Hadronization. Proceeding to systems with jets embedded in a medium, we study in-medium hadronization for jet showers. We quantify the effects of an ambient medium, focusing in particular on the dependence on the collective flow and size of the medium. Our results clarify the effects we expect from in-medium hadronization of jets on observables like fragmentation functions, hadron chemistry and jet shape.
We provide a first quantitative indication that the wave function of the proton contains unequal distributions of charm quarks and antiquarks, i.e. a nonvanishing intrinsic valence charm distribution. A significant nonvanishing valence component cannot be perturbatively generated, hence our results reinforce previous evidence that the proton contains an intrinsic (i.e., not radiatively generated) charm quark component. We establish our result through a determination of the parton distribution functions (PDFs) of charm quarks and antiquarks in the proton. We propose two novel experimental probes of this intrinsic charm valence component: D-meson asymmetries in Z+c-jet production at the LHCb experiment, and flavor-tagged structure functions at the Electron-Ion Collider.
This work explores the behaviour of a noncommutative harmonic oscillator in a time-dependent background, as previously investigated by Dey {\it et al.}\,\cite{Dey}. Specifically, we examine the system when expressed in terms of commutative variables, utilizing a generalized form of the standard Bopp-shift relations recently introduced by \cite{spb}. We solved the time dependent system and obtained the analytical form of the eigenfunction using Lewis' method of invariants, which is associated with the Ermakov-Pinney equation, a non-linear differential equation. We then explicitly provided the exact analytical solution set for the Ermakov-Pinney equation. Then, we computed the dynamics of the energy expectation value analytically and explored their graphical representations for various solution sets of the Ermakov-Pinney equation, associated with a particular choice of quantum number. Finally, we determined the generalized form of the uncertainty equality relations among the operators for both commutative and noncommutative cases. Expectedly, our study is consistent with the findings in \cite{Dey}, specifically in a particular limit where the coordinate mapping relations reduce to the standard Bopp-shift relations.
This paper gives an explicit isomorphic mapping from the 240 real $\mathbb{R}^{8}$ roots of the $E_8$ Gossett $4_{21}$ 8-polytope to two golden ratio scaled copies of the 120 root $H_4$ 600-cell quaternion 4-polytope using a traceless 8$\times$8 rotation matrix $\mathbb{U}$ with palindromic characteristic polynomial coefficients and a unitary form $e^{\text {i$\mathbb{U}$}}$. It also shows the inverse map from a single $H_4$ 600-cell to $E_8$ using a 4D$\hookrightarrow$8D chiral left$\leftrightarrow$right mapping function, $ \varphi$ scaling, and $\mathbb{U}^{-1}$. This approach shows that there are actually four copies of each 600-cell living within $E_8$ in the form of chiral $H_{4L}$$\oplus$$\varphi H_{4L}$$\oplus$$H_{4R}$$\oplus$$\varphi H_{4R}$ roots. In addition, it demonstrates a quaternion Weyl orbit construction of $H_4$-based 4-polytopes that provides an explicit mapping between $E_8$ and four copies of the tri-rectified Coxeter-Dynkin diagram of $H_4$, namely the 120-cell of order 600. Taking advantage of this property promises to open the door to as yet unexplored $E_8$-based Grand Unified Theories or GUTs.
Quantum gravitational effects become significant at a cut-off species scale that can be much lower than the Planck scale whenever we get a parametrically large number of fields becoming light. This is expected to occur at any perturbative limit of an effective field theory coupled to gravity, or equivalently, at any infinite distance limit in the field space of the quantum gravity completion. In this note, we present a universal pattern that links the asymptotic variation rates in field space of the quantum gravity cut-off $\Lambda_{\text{sp}}$ and the characteristic mass of the lightest tower of states $m$: $\frac{\vec\nabla m}{m} \cdot\frac{\vec\nabla \Lambda_{\rm sp}}{ \Lambda_{\rm sp}}=\frac1{d-2}$, where $d$ is the spacetime dimension. This restriction can be used to make more precise several Swampland criteria that constrain the effective field theories that can be consistently coupled to quantum gravity.
We analyze a model of qubits which we argue has an emergent quantum gravitational description similar to the fermionic Sachdev-Ye-Kitaev (SYK) model. The model we consider is known as the quantum $q$-spin model because it features $q$-local interactions between qubits. It was previously studied as a model of a quantum spin glass, and while we find that the model is glassy for $q=2$, $q=3$, and likely $q=4$, we also find evidence for previously unexpected SYK-like behavior for the quenched free energy down to the lowest temperatures for $q \geq 5$. This SYK-like physics includes power-law correlation functions and an extensive low temperature entropy, so we refer to the model as Spin SYK. The model is generic in that it includes all possible $q$-body couplings, lacks most symmetries, and has no spatial structure, so our results can be construed as establishing a certain ubiquity of quantum holography in systems dominated by many-body interactions. Furthermore, we discuss a generalized family of models which includes Spin SYK and which provably exhibit SYK-like physics in the solvable limit of large local Hilbert space dimension. We also comment on implications of a bosonic system with SYK-like properties for the study of holography, Hamiltonian complexity, and related topics.
Understanding the far-from-equilibrium dynamics of dissipative quantum systems, where dissipation and decoherence coexist with unitary dynamics, is an enormous challenge with immense rewards. Often, the only realistic approach is to forgo a detailed microscopic description and search for signatures of universal behavior shared by collections of many distinct, yet sufficiently similar, complex systems. Quantum chaos provides a powerful statistical framework for addressing this question, relying on symmetries to obtain information not accessible otherwise. This thesis examines how to reconcile chaos with dissipation, proceeding along two complementary lines. In Part I, we apply non-Hermitian random matrix theory to open quantum systems with Markovian dissipation and discuss the relaxation timescales and steady states of three representative examples of increasing physical relevance: single-particle Lindbladians and Kraus maps, open free fermions, and dissipative Sachdev-Ye-Kitaev (SYK) models. In Part II, we investigate the symmetries, correlations, and universality of many-body open quantum systems, classifying several models of dissipative quantum matter. From a theoretical viewpoint, this thesis lays out a generic framework for the study of the universal properties of realistic, chaotic, and dissipative quantum systems. From a practical viewpoint, it provides the concrete building blocks of dynamical dissipative evolution constrained by symmetry, with potential technological impact on the fabrication of complex quantum structures. (Full abstract in the thesis.)
We derive the exact actions of the $Q$-state Potts model valid on any graph, first for the spin degrees of freedom, and second for the Fortuin-Kasteleyn clusters. In both cases the field is a traceless $Q$-component scalar field $\Phi^\alpha$. For the Ising model ($Q=2$), the field theory for the spins has upper critical dimension $d_{\rm c}^{\rm spin}=4$, whereas for the clusters it has $d_{\rm c}^{\rm cluster}=6$. As a consequence, the probability for three points to be in the same cluster is not given by mean-field theory theory for $d$ within $4<d<6$. We estimate the associated universal structure constant as $C=\sqrt{6-d}+ {\cal O}(6-d)^{3/2}$. This shows that some observables in the Ising model have an upper critical dimension of 4, while others have an upper critical dimension of $6$. Combining perturbative results from the $\epsilon=6-d$ expansion with a non-perturbative treatment close to dimension $d=4$ allows us to locate the shape of the critical domain of the Potts model in the whole $(Q,d)$ plane.
Infinite distance limits in the moduli space of a quantum gravity theory are characterized by having infinite towers of states becoming light, as dictated by the Distance Conjecture in the Swampland program. These towers imply a drastic breakdown in the perturbative regimes of the effective field theory at a quantum gravity cut-off scale known as the species scale. In this paper, we find a universal pattern satisfied in all known infinite distance limits of string theory compactifications, which relates the variation in field space of the mass of the tower and the species scale: $\frac{\vec\nabla m}{m} \cdot\frac{\vec\nabla \Lambda_{\rm sp}}{ \Lambda_{\rm sp}}=\frac1{\sqrt{d-2}}$ in $d$ spacetime dimensions. This implies a more precise definition of the Distance conjecture and sharp bounds for the exponential decay rates. We provide plethora of evidence in string theory and identify some sufficient conditions that allow the pattern to hold from a bottom-up perspective.
We investigate the massive Sine-Gordon model in the finite ultraviolet regime on the two-dimensional Minkowski spacetime $(\mathbb{R}^2,\eta)$ with an additive Gaussian white noise. In particular we construct the expectation value and the correlation functions of a solution of the underlying stochastic partial differential equation (SPDE) as a power series in the coupling constant, proving ultimately uniform convergence. This result is obtained combining an approach first devised in [11] to study SPDEs at a perturbative level with the one discussed in [4] to construct the quantum sine-Gordon model using techniques proper of the perturbative, algebraic approach to quantum field theory (pAQFT). At a formal level the relevant expectation values are realized as the evaluation of suitably constructed functionals over $C^\infty(\mathbb{R}^2)$. In turn, these are elements of a distinguished algebra whose product is a deformation of the pointwise one, by means of a kernel which is a linear combination of two components. The first encompasses the information of the Feynmann propagator built out of an underlying Hadamard, quantum state, while the second encodes the correlation codified by the Gaussian white noise. In our analysis, first of all we extend the results obtained in [3,4] proving the existence of a convergent modified version of the S-matrix and of an interacting field as elements of the underlying algebra of functionals. Subsequently we show that it is possible to remove the contribution due to the Feynmann propagator by taking a suitable $\hbar\to 0^+$-limit, hence obtaining the sought expectation value of the solution and of the correlation functions of the SPDE associated to the stochastic Sine-Gordon model.
Analyzing the representations of the Lorentz group, we give a systematic count and construction of all the possible Lagrangians describing an antisymmetric rank two tensor field. The count yields two scalars: the gauge invariant Kalb-Ramond model, equivalent to the sigma model and familiar from super gravity and string theory, and the conformally invariant Avdeev-Chizhov model, which describes self-dual tensors. The count also includes a third invariant, a pseudoscalar, which is an antisymmetrized form of the Avdeev-Chizhov Lagrangian, first noticed in the $SU(2/1)$ superalgebraic model of the weak interactions. This model is also conformally invariant, and naturally implements the Landau $CP$ symmetry. Then, by extending the Duffin-Kemmer-Petiau 10 component formalism, we recover the model Lagrangians as first order systems. To complete the analysis we classify all local Lorentz invariant potentials (mass terms and quartic couplings) for charged antisymmetric tensor fields coupled to a Yang-Mills field.
Two theories describing antisymmetric tensor fields in 4 dimensions are well known: the gauge invariant Kalb-Ramond model which generalizes the Maxwell Lagrangian and the Avdeev-Chizhov model which describes self-dual 2-tensors. Using a theorem of Jackiw and Pi, we study p-forms in D dimensions and prove that the Kalb-Ramond model is conformal invariant only when the rank p of the gauge tensor is equal to its canonical dimension (D-2)/2 and that the Avdeev-Chizhov model and its new CP generalization inspired by the SU(2/1) superalgebraic chiral structure of the electroweak interactions are both conformal invariant in any even dimension.
We have constructed a generative artificial intelligence model to predict dual gravity solutions when provided with the input of holographic entanglement entropy. The model utilized in our study is based on the transformer algorithm, widely used for various natural language tasks including text generation, summarization, and translation. This algorithm possesses the ability to understand the meanings of input and output sequences by utilizing multi-head attention layers. In the training procedure, we generated pairs of examples consisting of holographic entanglement entropy data and their corresponding metric solutions. Once the model has completed the training process, it demonstrates the ability to generate predictions regarding a dual geometry that corresponds to the given holographic entanglement entropy. Subsequently, we proceed to validate the dual geometry to confirm its correspondence with the holographic entanglement entropy data.
A simplicial framework for the gerbe-theoretic modelling of supercharged-loop dynamics in the presence of worldsheet defects is discussed whose equivariantisation with respect to global supersymmetries of the bulk theory and subsequent orbit decomposition lead to a natural stratification of and cohomological superselection rules for target-space supergeometry, expected to encode essential information on the quantised 2$d$ field theory. A physically relevant example is analysed in considerable detail.
We investigate the symmetry-breaking effect on the spectral function of holographic fermions. We found analytic expressions of fermion Green's functions in the probe-limit by considering various types of Lorentz symmetry breaking order parameter fields. These analytic results agree with numerical results. We also study the effect of choices of fermion components, which is known as holographic quantization. We find that there are no spectral dualities in $AdS_5$ unlike in $AdS_4$. We determined the shapes and singularity types observed in each Green's function. We finally calculate the fermions spectral function in the full backreacted background and then compare it with the analytic results to show the reliability of analytic results in the probe limit.
Assuming the von Neumann algebra associated with a generic de Sitter observer is properly infinite (type III) we use Connes cocycle to identify the unique ( up to unitary equivalence) background independent dominant weight on an extended algebra formally including an external observer. The background independent algebra defined as the centralizer of this dominant weight is equipped with a semi finite trace. Quantum gravity effects, as well as an algebraic version of the no boundary Hartle Hawking partition function, can be defined by representing, classically different de Sitter closed Universes, as equivalence classes of finite projections in the background independent algebra. The associated generalized entropy is determined by the value of the semi finite trace on each equivalence class of finite projections.
Entanglement contour and R\'{e}nyi contour reflect the real-space distribution of entanglement entropy, serving as the fine structure of entanglement. In this work, we unravel the hyperfine structure by rigorously decomposing R\'{e}nyi contour into the contributions from particle-number cumulants. We show that the hyperfine structure, introduced as a quantum-information concept, has several properties, such as additivity, normalization, symmetry, and unitary invariance. To extract the underlying physics of the hyperfine structure, we numerically study lattice fermion models with mass gap, critical point, and Fermi surface, and observe that different behaviors appear in the contributions from higher-order particle-number cumulants. We also identify exotic scaling behaviors in the case of mass gap with nontrivial topology, signaling the existence of topological edge states. In conformal field theory (CFT), we derive the dominant hyperfine structure of both R\'{e}nyi entropy and refined R\'{e}nyi entropy. By employing the AdS$_3$/CFT$_2$ correspondence, we find that the refined R\'{e}nyi contour can be holographically obtained by slicing the bulk extremal surfaces. The extremal surfaces extend outside the entanglement wedge of the corresponding extremal surface for entanglement entropy, which provides an exotic tool to probe the hyperfine structure of the subregion-subregion duality in the entanglement wedge reconstruction. This paper is concluded with an experimental protocol and interdisciplinary research directions for future study.
We construct a multiverse model based on a recent proposal for dS wedge holography, where empty AdS$_3$ space is cut off by a pair of accelerated dS$_2$ space universes, one near the AdS boundary, denoted the UV brane, and one in the AdS interior, the IR brane. We glue together several copies of this configuration along the UV and IR branes in a periodic matter. To provide the model with dynamics of the like near Nariai black holes used in other multiverse toy models, we add dS JT gravity as an intrinsic gravity theory on the IR branes. We then study the entanglement entropy with respect to a UV brane observer, who finds a Page curve transition due to an entanglement island connecting the UV and IR branes. This process involves the coarse-graining of information outside the causally accessible region to the observer. Our model provides an explicit realization of entanglement between IR and UV degrees of freedom encoded in the multiverse.
Earlier results show that the N = 1/2 supersymmetric path integral on a closed even dimensional Riemannian spin manifold (X,g) can be constructed in a mathematically rigorous way via Chen differential forms and techniques from non-commutative geometry, if one considers it as a current on the smooth loop space of X. This construction admits a Duistermaat-Heckman localization formula. In this note, fixing a topological spin structure on X, we prove that any smooth family of Riemannian metrics on X canonically induces a Chern-Simons current which fits into a transgression formula for the supersymmetric path integral. In particular, this result entails that the supersymmetric path integral induces a differential topological invariant on X, which essentially stems from the A-hat-genus of X.
We study the large $N$ limit of some supersymmetric partition functions of the $\mathrm{U}(N)_{k}\times \mathrm{U}(N)_{-k}$ ABJM theory computed by supersymmetric localization. We conjecture an explicit expression, valid to all orders in the large $N$ limit, for the partition function on the $\mathrm{U}(1)\times \mathrm{U}(1)$ invariant squashed sphere in the presence of real masses in terms of an Airy function. Several non-trivial tests of this conjecture are presented. In addition, we derive an explicit compact expression for the topologically twisted index of the ABJM theory valid at fixed $k$ to all orders in the $1/N$ expansion. We use these results to derive the topologically twisted index and the sphere partition function in the 't Hooft limit which correspond to genus $\tt g$ type IIA string theory free energies to all orders in the $\alpha'$ expansion. We discuss the implications of our results for holography and the physics of AdS$_4$ black holes.
We study the $S^1\times\Sigma_{\mathfrak g}$ topologically twisted index and the squashed sphere partition function of various 3d $\mathcal N\geq2$ holographic superconformal field theories arising from M2-branes. Employing numerical techniques in combination with well-motivated conjectures we provide compact closed-form expressions valid to all orders in the perturbative $1/N$ expansion for these observables. We also discuss the holographic implications of our results for the topologically twisted index for the dual M-theory Euclidean path integral around asymptotically AdS$_4$ solutions of 11d supergravity. In Lorentzian signature this leads to a prediction for the corrections to the Bekenstein-Hawking entropy of a class of static asymptotically AdS$_4$ BPS black holes.
We show that out-of-time-order correlators (OTOCs) constitute a probe for Local-Operator Entanglement (LOE). There is strong evidence that a volumetric growth of LOE is a faithful dynamical indicator of quantum chaos, while OTOC decay corresponds to operator scrambling, often conflated with chaos. We show that rapid OTOC decay is a necessary but not sufficient condition for linear (chaotic) growth of the LOE entropy. We analytically support our results through wide classes of local-circuit models of many-body dynamics, including both integrable and non-integrable dual-unitary circuits. We show sufficient conditions under which local dynamics leads to an equivalence of scrambling and chaos.
We construct, following \cite{mpgm14,mpgm17}, a massive M2-brane (supermembrane) as the limit of a genus two M2-brane that becomes a twice punctured Riemann surface with particular boundary conditions on the fields defined on the punctures. The target space is $M_9\times LCD$, where $LCD$ is a genus one light cone diagram. It contains mass terms and a topological term associated with the non-triviality of the target surface that, at low energies, can be associated with the presence of a cosmological constant. We show that the supergravity background of the M2-brane considered in this formulation requires the presence of M9-branes acting as sources. They correspond to the 11D uplift of the characteristic D8's of Romans supergravity. To this end, we explicitly show that some of the background singularities of the massive M2-brane can be reproduced by the M9-branes found by \cite{Bergshoeff}. This establishes a relation between the Romans mass and the moduli of the massive M2-brane. When dimensionally reduced, we obtain a worldsheet Hamiltonian of a N=2 type IIA closed superstring in 10D. We denote it \textit{massive} string. The corresponding \textit{massive} string inherits a non-vanishing constant term from the topological massive M2-brane that shifts the Hamiltonian. The non-vanishing parameter is related to the non-trivial structure of the massive M2-brane background and it can be related to the Romans mass term. It also contains a modified tension due to the non-trivial dependence on the moduli and on the punctures associated with the target torus.
A coupled massive Thirring model of two interacting Dirac spinors in $1+1$ dimensions with fields taking values in a Grassmann algebra is introduced, which is closely related to a SU(1,1) version of the Grassmannian Thirring model also introduced in this work. The Lax pair for the system is constructed, and its equations of motion are obtained from a zero curvature condition. It is shown that the system possesses several infinite hierarchies of conserved quantities, which strongly confirms its integrability. The model admits a canonical formulation and is invariant under space-time translations, Lorentz boosts and global U(1) gauge transformations, as well as discrete symmetries like parity and time reversal. The conserved quantities associated to the continuous symmetries are derived using Noether's theorem, and their relation to the lower-order integrals of motion is spelled out. New nonlocal integrable models are constructed through consistent nonlocal reductions between the field components of the general model. The Lagrangian, the Hamiltonian, the Lax pair and several infinite hierarchies of conserved quantities for each of these nonlocal models are obtained substituting its reduction in the expressions of the analogous quantities for the general model. It is shown that, although the Lorentz symmetry of the general model breaks down for its nonlocal reductions, these reductions remain invariant under parity, time reversal, global U(1) gauge transformations and space-time translations.
We introduce a framework for quantifying random matrix behavior of 2d CFTs and AdS$_3$ quantum gravity. We present a 2d CFT trace formula, precisely analogous to the Gutzwiller trace formula for chaotic quantum systems, which originates from the $SL(2,\mathbb{Z})$ spectral decomposition of the Virasoro primary density of states. An analogy to Berry's diagonal approximation allows us to extract spectral statistics of individual 2d CFTs by coarse-graining, and to identify signatures of chaos and random matrix universality. This leads to a necessary and sufficient condition for a 2d CFT to display a linear ramp in its coarse-grained spectral form factor. Turning to gravity, AdS$_3$ torus wormholes are cleanly interpreted as diagonal projections of squared partition functions of microscopic 2d CFTs. The projection makes use of Hecke operators. The Cotler-Jensen wormhole of AdS$_3$ pure gravity is shown to be extremal among wormhole amplitudes: it is the minimal completion of the random matrix theory correlator compatible with Virasoro symmetry and $SL(2,\mathbb{Z})$-invariance. We call this MaxRMT: the maximal realization of random matrix universality consistent with the necessary symmetries. Completeness of the $SL(2,\mathbb{Z})$ spectral decomposition as a trace formula allows us to factorize the Cotler-Jensen wormhole, extracting the microscopic object $Z_{\rm RMT}(\tau)$ from the coarse-grained product. This captures details of the spectrum of BTZ black hole microstates. $Z_{\rm RMT}(\tau)$ may be interpreted as an AdS$_3$ half-wormhole. We discuss its implications for the dual CFT and modular bootstrap at large central charge.
In this work, we consider the gravitational baryogenesis in the framework of non-minimal derivative coupling model. A mechanism to generate the baryon asymmetry based on the coupling between the derivative of the Ricci scalar curvature and the baryon current in context of non-minimal derivative coupling model is investigated. We show that, in this model, the temperature increases during the reheating periods to the end of reheating period or beginning of radiation dominated era. Therefore the reheating temperature is larger then decoupling temperature. It can be demonstrated that, the evaluation of baryon asymmetry is not depends on coupling constant. In this model we can generate baryon asymmetry at low and high reheating temperature, by considering the high friction constraint.
We consider $\text{SU}(2)$ quantum chromodynamics in $1+1$ dimensions with a single quark in the spin $J$ representation of the gauge group and study the theory in the large $J$ limit where the gauge coupling $g^2 \to 0$ and $J \to \infty$ with $\lambda = g^2 J^2$ fixed. We work with a Dirac spinor field for arbitrary $J$, and with a Majorana spinor for integer $J$ since the integer spin representations of $\text{SU}(2)$ are real, and analyse the two cases separately. The theory is reformulated in terms of global color non-singlet fermion bilocal operators which satisfy a $W_\infty \times \text{U}(2J+1)$ algebra. In the large $J$ limit, the dynamics of the bilocal fields is captured by fluctuations along a particular coadjoint orbit of the $W_\infty$ algebra. We show that the global colour-singlet sector of the bilocal field fluctuations satisfy the same integral equation for meson wavefunctions that appears in the 't Hooft model. For Majorana spinors in the integer spin $J$ representation, the Majorana condition projects out half of the meson spectrum, as a result of which the linear spacing of the asymptotic meson spectrum for Majorana fermions is double that of Dirac fermions. The Majorana condition also projects out the zero mass bound state that is present for the Dirac quark at zero quark mass. We also consider the formulation of the model in terms of local charge densities and compute the quark spectral function in the large $J$ limit: we see evidence for the absence of a pole in the quark propagator.
I discuss the recent progress in bypassing the KPZ barrier for the existence of nonperturbative bosonic strings in $1<d<25$. I consider string anomalies which emerge from higher terms of the DeWitt-Seeley expansion as $\varepsilon \times \varepsilon^{-1}$ with $\varepsilon$ being a UV cutoff. I show they give a nonvanishing contribution to the central charge and to the string susceptibility, telling the Nambu-Goto and Polyakov strings apart. I describe an exact solution of the emerging four-derivative two-dimensional conformal theory and its relation to minimal models. Talk at "Gravity, Strings and Fields: A Conference in Honour of Gordon Semenoff", Montreal July 24-28, 2023.
The fraction of $\chi_{c1}$ and $\chi_{c2}$ decays in the prompt $J/\psi$ yield, $F_{\chi c}=\sigma_{\chi_c \to J/\psi}/\sigma_{J/\psi}$, is measured by the LHCb detector in pPb collisions at $\sqrt{s_{NN}}=8.16$ TeV. The study covers the forward ($1.5<y^*<4.0$) and backward ($-5.0<y^*<-2.5$) rapidity regions, where $y^*$ is the $J/\psi$ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 $\pm$ 0.3 nb$^{-1}$ and 20.8 $\pm$ 0.5 nb$^{-1}$, respectively. The result is presented as a function of the $J/\psi$ transverse momentum $p_{T,J/\psi}$ in the range 1$<p_{T, J/\psi}<20$ GeV/$c$. The $F_{\chi c}$ fraction at forward rapidity is compatible with the LHCb measurement performed in $pp$ collisions at $\sqrt{s}=7$ TeV, whereas the result at backward rapidity is 2.4 $\sigma$ larger than in the forward region for $1<p_{T, J/\psi}<3$ GeV/$c$. The increase of $F_{\chi c}$ at low $p_{T, J/\psi}$ at backward rapidity is compatible with the suppression of the $\psi$(2S) contribution to the prompt $J/\psi$ yield. The lack of in-medium dissociation of $\chi_c$ states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation.
This contribution presents a pragmatic approach to read-out electronics for drift chambers used in particle physics experiments, specifically for the R3B experiment at GSI. The design uses discrete miniature SMD components and LVDS inputs of a low-cost FPGA to achieve a performance similar to classic ASIC solutions to the problem. The circuit comprises a high gain, low noise amplifier, a custom signal shaper, tailored to the specifics of proportional counter signals, and a leading-edge discriminator with programmable threshold. The presented approach offers an attractive solution for small to medium sized detector systems that require specialized read-out electronics but cannot afford the high cost and development effort associated with ASICs.
Maintaining the required performance of the CMS electromagnetic calorimeter (ECAL) barrel at the High-Luminosity Large Hadron Collider (HL-LHC) requires the replacement of the entire on-detector electronics. 12240 new very front end (VFE) cards will amplify and digitize the signals of 62100 lead-tungstate crystals instrumented with avalanche photodiodes. The VFE cards host five channels of CATIA pre-amplifier ASICs followed by LiTE-DTU ASICs, which digitize signals with 160MS/s and 12bit resolution. We present the strategy and infrastructure developed for achieving the required reliability of less than 0.5% failing channels over the expected lifetime of 20 years. This includes the choice of standards, design for reliability and manufacturing, as well as factory acceptance tests, reception testing, environmental stress screening and calibration of the VFE cards.
Low gain avalanche detectors (LGADs) deliver excellent timing resolution, which can mitigate mis-assignment of vertices associated with pileup at the High Luminosity LHC and other future hadron colliders. The most highly irradiated LGADs will be subject to $2.5 \times10^{15} \mathrm{n}_\mathrm{eq} \mathrm{cm}^{-2}$ of hadronic fluence during HL-LHC operation; their performance must tolerate this. Hamamatsu Photonics K.K. and Fondazione Bruno Kessler LGADs have been irradiated with 400 and 500 MeV protons respectively in several steps up to $1.5 \times10^{15} \mathrm{n}_\mathrm{eq} \mathrm{cm}^{-2}$. Measurements of the acceptor removal constants of the gain layers, evolution of the timing resolution and charge collection with damage, and inter-channel isolation characteristics, for a variety of design options, are presented here.
This work describes an online processing pipeline designed to identify anomalies in a continuous stream of data collected without external triggers from a particle detector. The processing pipeline begins with a local reconstruction algorithm, employing neural networks on an FPGA as its first stage. Subsequent data preparation and anomaly detection stages are accelerated using GPGPUs. As a practical demonstration of anomaly detection, we have developed a data quality monitoring application using a cosmic muon detector. Its primary objective is to detect deviations from the expected operational conditions of the detector. This serves as a proof-of-concept for a system that can be adapted for use in large particle physics experiments, enabling anomaly detection on datasets with reduced bias.
This letter presents a measurement of the nuclear modification factor of large-radius jets in $\sqrt{s_\mathrm{NN}} = 5.02$ TeV Pb+Pb collisions by the ATLAS experiment. The measurement is performed using 1.72 nb$^{-1}$ and 257 pb$^{-1}$ of Pb+Pb and $pp$ data, respectively. The large-radius jets are reconstructed with the anti-$k_{t}$ algorithm using a radius parameter of $R = 1.0$, by re-clustering anti-$k_{t}$ $R = 0.2$ jets, and are measured over the transverse momentum ($p_{\mathrm{T}}$) kinematic range of $158 < p_{\mathrm{T}} < 1000$ GeV and absolute pseudorapidity $|y|<2.0$. The large-radius jet constituents are further re-clustered using the $k_{t}$ algorithm in order to obtain the splitting parameters, $\sqrt{d_{12}}$ and $\Delta R_{12}$, which characterize the transverse momentum scale and angular separation for the hardest splitting in the jet, respectively. The nuclear modification factor, $R_{\mathrm{AA}}$, obtained by comparing the Pb+Pb jet yields to those in $pp$ collisions, is measured as a function of jet transverse momentum ($p_{\mathrm{T}}$) and $\sqrt{d_{12}}$ or $\Delta R_{12}$. A significant difference in the quenching of large-radius jets having single sub-jet and those with more complex substructure is observed. Systematic comparison of jet suppression in terms of $R_{\mathrm{AA}}$ for different jet definitions is also provided. Presented results support the hypothesis that jets with hard internal splittings lose more energy through quenching and provide a new perspective for understanding the role of jet structure in jet suppression.
The heavy-ion collisions (A--A) at the Large Hadron Collider (LHC) energies have confirmed the production of the quark-gluon plasma (QGP), a new state of nuclear matter where quarks and gluons are deconfined. The light-flavour hadrons ($\pi$, K, p), constitute the bulk of the produced particles, carry useful information of the collision geometry, collective behaviour and thermal property of the QGP. The measurements of light-flavour hadron production in small collision systems (pp and p--A) at the LHC energies have shown the onset of collective phenomena (e.g. radial flow and long-range correlations) that resemble what is typically observed in nucleus-nucleus collisions and attributed to the formation of a deconfined system of quarks and gluons. The new results of the identified light-flavour particle production measured in high-multiplicity triggered pp collisions at $\sqrt{s}=13$~TeV of ALICE Run 2 will be presented in search of collective behaviour in small collision systems. The transverse momenta $p_{\rm T}$-spectra of the identified particles show hardening at the mid-$p_{\rm T}$. The mean transverse momenta ($\langle p_{\rm T} \rangle$) are shown as a function of charged-particle multiplicity. The ratios of $p_{\rm T}$-spectra and the ratios of the integrated yields of kaon- and proton-to-pion are also presented and compared with published results.
Photon-resolved Floquet theory keeps track of the photon exchange of a quantum system with a coherent driving field. It thus complements the standard full-counting statistics that counts the number of photons exchanged with incoherent photon modes giving rise to dissipation. In this paper, we introduce a unifying framework describing both situations. We develop methods suitable for an analytical evaluation of low-order cumulants of photonic probability distributions. Within this framework we analyze the two-mode Jaynes-Cummings model to demonstrate that the Photon-resolved Floquet theory and the standard full-counting statistics make consistent statistical predictions. Interestingly, we find that the photon-flux fluctuations diverge for vanishing dissipation, which can be related to an entanglement effect between the driven matter system and the driving field. To substantiate our results, we use our framework to describe efficient photon up-conversion in an ac-driven lambda system, that is characterized by a high signal-to-noise ratio. As the framework is non-perturbative and predicts fluctuations, it paves the way towards non-perturbative spectroscopy, which will assist to improve metrological methods.
Classical simulation of quantum computers is an irreplaceable step in the design of quantum algorithms. Exponential simulation costs demand the use of high-performance computing techniques, and in particular distribution, whereby the quantum state description is partitioned between a network of cooperating computers - necessary for the exact simulation of more than approximately 30 qubits. Distributed computing is notoriously difficult, requiring bespoke algorithms dissimilar to their serial counterparts with different resource considerations, and which appear to restrict the utilities of a quantum simulator. This manuscript presents a plethora of novel algorithms for distributed full-state simulation of gates, operators, noise channels and other calculations in digital quantum computers. We show how a simple, common but seemingly restrictive distribution model actually permits a rich set of advanced facilities including Pauli gadgets, many-controlled many-target general unitaries, density matrices, general decoherence channels, and partial traces. These algorithms include asymptotically, polynomially improved simulations of exotic gates, and thorough motivations for high-performance computing techniques which will be useful for even non-distributed simulators. Our results are derived in language familiar to a quantum information theory audience, and our algorithms formalised for the scientific simulation community. We have implemented all algorithms herein presented into an isolated, minimalist C++ project, hosted open-source on Github with a permissive MIT license, and extensive testing. This manuscript aims both to significantly improve the high-performance quantum simulation tools available, and offer a thorough introduction to, and derivation of, full-state simulation techniques.
Using quantum systems as sensors or probes has been shown to greatly improve the precision of parameter estimation by exploiting unique quantum features such as entanglement. A major task in quantum sensing is to design the optimal protocol, i.e., the most precise one. It has been solved for some specific instances of the problem, but in general even numerical methods are not known. Here, we focus on the single-shot Bayesian setting, where the goal is to find the optimal initial state of the probe (which can be entangled with an auxiliary system), the optimal measurement, and the optimal estimator function. We leverage the formalism of higher-order operations to develop a method based on semidefinite programming that finds a protocol that is close to the optimal one with arbitrary precision. Crucially, our method is not restricted to any specific quantum evolution, cost function or prior distribution, and thus can be applied to any estimation problem. Moreover, it can be applied to both single or multiparameter estimation tasks. We demonstrate our method with three examples, consisting of unitary phase estimation, thermometry in a bosonic bath, and multiparameter estimation of an SU(2) transformation. Exploiting our methods, we extend several results from the literature. For example, in the thermometry case, we find the optimal protocol at any finite time and quantify the usefulness of entanglement. Additionally, we show that when the cost function is the mean squared error, projective measurements are optimal for estimation.
A variational quantum algorithm for numerically solving partial differential equations (PDEs) on a quantum computer was proposed by Lubasch et al. In this paper, we generalize the method introduced by Lubasch et al. to cover a broader class of nonlinear PDEs as well as multidimensional PDEs, and study the performance of the variational quantum algorithm on several example equations. Specifically, we show via numerical simulations that the algorithm can solve instances of the Single-Asset Black-Scholes equation with a nontrivial nonlinear volatility model, the Double-Asset Black-Scholes equation, the Buckmaster equation, and the deterministic Kardar-Parisi-Zhang equation. Our simulations used up to $n=12$ ansatz qubits, computing PDE solutions with $2^n$ grid points. We also performed proof-of-concept experiments with a trapped-ion quantum processor from IonQ, showing accurate computation of two representative expectation values needed for the calculation of a single timestep of the nonlinear Black--Scholes equation. Through our classical simulations and experiments on quantum hardware, we have identified -- and we discuss -- several open challenges for using quantum variational methods to solve PDEs in a regime with a large number ($\gg 2^{20}$) of grid points, but also a practical number of gates per circuit and circuit shots.
The work here enables quasi-linear cost-scaling with $t$ while keeping ${\rm polylog} (1/\epsilon)$ scaling and no extra block-encoding qubits, where $\epsilon$ is the algorithmic error. This work opens up the possibility for off-loading signal processing with the use of low-weight Fourier expansion which avoids the Gibbs phenomenon and has low $1$-norm on the coefficients.
Quantum metrology takes advantage of quantum correlations to enhance the sensitivity of sensors and measurement techniques beyond their fundamental classical limit given by the shot noise limit. The use of both temporal and spatial correlations present in quantum states of light can extend quantum-enhanced sensing to a parallel configuration that can simultaneously probe an array of sensors or independently measure multiple parameters. To this end, we use multi-spatial mode twin beams of light, which are characterized by independent quantum-correlated spatial subregions in addition to quantum temporal correlations, to probe a four-sensor quadrant plasmonic array. We show that it is possible to independently and simultaneously measure local changes in refractive index for all four sensors with a quantum enhancement in sensitivity in the range of $22\%$ to $24\%$ over the corresponding classical configuration. These results provide a first step towards highly parallel spatially resolved quantum-enhanced sensing techniques and pave the way toward more complex quantum sensing and quantum imaging platforms.
We present an approach to achieve zero modes in lattice models that do not rely on any symmetry or topology of the bulk, which are robust against disorder in the bulk of any type and strength. Such symmetry-free zero modes (SFZMs) are formed by attaching a single site or small cluster with zero mode(s) to the bulk, which serves as the "nucleus" that expands to the entire lattice. We identify the requirements on the couplings between this boundary and the bulk, which reveals that this approach is intrinsically non-Hermitian. We then provide several examples with either an arbitrary or structured bulk, forming spectrally embedded zero modes in the bulk continuum, midgap zero modes, and even restoring the "zeroness" of coupling or disorder-shifted topological corner states. Focusing on viable realizations using photonic lattices, we show that the resulting SFZM can be observed as the single lasing mode when optical gain is applied to the boundary.
We present a security proof for variable-length QKD in the Renner framework against IID collective attacks. Our proof can be lifted to coherent attacks using the postselection technique. Our first main result is a theorem to convert a series of security proofs for fixed-length protocols satisfying certain conditions to a security proof for a variable-length protocol. This conversion requires no new calculations, does not require any changes to the final key lengths or the amount of error-correction information, and at most doubles the security parameter. Our second main result is the description and security proof of a more general class of variable-length QKD protocols, which does not require characterizing the honest behaviour of the channel connecting the users before the execution of the QKD protocol. Instead, these protocols adaptively determine the length of the final key, and the amount of information to be used for error-correction, based upon the observations made during the protocol. We apply these results to the qubit BB84 protocol, and show that variable-length implementations lead to higher expected key rates than the fixed-length implementations.
Sub-harmonics of electric dipole spin resonance (EDSR) mediated by Landau-Zener-St{\"u}ckelberg-Majorana (LZSM) tunneling transitions are studied numerically and analytically in a Zeeman-split four level system with strong spin-orbit coupling that can be realized, for example, in a GaAs-based double quantum dot in a single-hole regime. The spin qubit is formed in one of the dots and the second dot is used as an auxiliary element to enhance functionality of the spin qubit. In particular, it is found that the spin rotation rate can be essentially enhanced due to the tunnel coupling with the auxiliary dot on both the main EDSR frequency and at its high sub-harmonics allowing the coherent spin $\pi$-rotations on a 10-ns time scale. Spin manipulation on high sub-harmonics is promising for new time-efficient schemes of the spin control and readout in qubit devices operating at high magnetic fields where the main harmonic is inaccessible due to hardware limitations.
The quantum Zeno effect asserts that quantum measurements inhibit simultaneous unitary dynamics when the "collapse" events are sufficiently strong and frequent. This applies in the limit of strong continuous measurement or dissipation. It is possible to implement a dissipative control that is known as "Zeno Dragging", by dynamically varying the monitored observable, and hence also the eigenstates which are attractors under Zeno dynamics. This is similar to adiabatic processes, in that the Zeno dragging fidelity is highest when the rate of eigenstate change is slow compared to the measurement rate. We demonstrate here two methods for using such dynamics to achieve control of quantum systems. The first, which we shall refer to as "shortcut to Zeno", is analogous to the shortcuts to adiabaticity (counterdiabatic driving) that are frequently used to accelerate unitary adiabatic evolution. In the second approach we apply the Chantasri Dressel Jordan (2013, CDJ) stochastic action, and demonstrate that the extremal-probability readout paths derived from this are well suited to setting up a Pontryagin-style optimization of the Zeno dragging schedule. Implementing these methods on the Zeno dragging of a qubit, we find that both approaches yield the same solution, namely, that the optimal control is a unitary that matches the motion of the Zeno-monitored eigenstate. These methods open up new pathways toward systematically developing dynamic control of Zeno subspaces to realize dissipatively-stabilized quantum operations.
Recently, a Hamiltonian dynamics simulation was performed on a kicked ferromagnetic 2D transverse field Ising model with a connectivity graph native to the 127 qubit heavy-hex IBM Quantum architecture using ZNE quantum error mitigation. We demonstrate that one of the observables in this Trotterized Hamiltonian dynamics simulation, namely magnetization, can be efficiently simulated on current superconducting qubit-based programmable quantum annealing computers. We show this using two distinct methods: reverse quantum annealing and h-gain state encoding. This simulation is possible because the 127 qubit heavy-hex connectivity graph can be natively embedded onto the D-Wave Pegasus quantum annealer hardware graph and because there exists a direct equivalence between the energy scales of the two types of quantum computers. We derive equivalent anneal pauses in order to simulate the Trotterized quantum circuit dynamics for varying Rx rotations $\theta_h \in (0, \frac{\pi}{2}]$, using quantum annealing processors. Multiple disjoint instances of the Ising model of interest can be embedded onto the D-Wave Pegasus hardware graph, allowing for parallel quantum annealing. We report equivalent magnetization dynamics using quantum annealing for time steps of 20, 50 up to 10,000, which we find are consistent with exact classical 27 qubit heavy-hex Trotterized circuit magnetization dynamics, and we observe reasonable, albeit noisy, agreement with the existing simulations for single site magnetization at 20 Trotter steps. The quantum annealers are able to simulate equivalent magnetization dynamics for thousands of time steps, significantly out of the computational reach of the digital quantum computers on which the original Hamiltonian dynamics simulations were performed.
This paper presents a comparative analysis of three routing strategies in opportunistic quantum networks. Quantum communication networks face unique challenges, such as the fragility of qubits and the need to create and maintain pairs of entangled states for reliable transmission. In this context, efficient and reliable routing is crucial to maximize the fidelity of the established routes, minimize the creation of new entangled pairs, and reduce the need for route recalculation. The routing strategies are compared based on the fidelity of the chosen routes, the number of entangled pairs created, and the number of route recalculations. The results obtained provide valuable information for the design and optimization of opportunistic quantum networks, contributing to advances in the efficiency and reliability of quantum communications.
Millimeter-wave superconducting resonators are a useful tool for studying quantum device coherence in a new frequency domain. However, improving resonators is difficult without a robust and reliable method for coupling millimeter-wave signals to 2D structures. We develop and characterize a tapered transition structure coupling a rectangular waveguide to a planar slotline waveguide with better than 0.5 dB efficiency over 14 GHz, and use it to measure ground-shielded resonators in the W band (75-110 GHz). Having decoupled the resonators from radiative losses, we consistently achieve single-photon quality factors above $10^5$, with a two-level-system loss limit above $10^6$, and verify the effectiveness of oxide removal treatments to reduce loss. These values are 4-5 times higher than those previously reported in the W band, and much closer to typical planar microwave devices, demonstrating the potential for low-loss on-chip millimeter wave quantum technology.
Entanglement constitutes one of the key concepts in quantum mechanics and serves as an indispensable tool in the understanding of quantum many-body systems. In this work, we perform extensive numerical investigations of extensive entanglement properties of coupled quantum spin chains. This setup has proven useful for e.g. extending the Lieb-Schultz-Mattis theorem to open systems, and contrasts the majority of previous research where the entanglement cut has one lower dimension than the system. We focus on the cases where the entanglement Hamiltonian is either gapless or exhibits spontaneous symmetry breaking behavior. We further employ conformal field theoretical formulae to identify the universal behavior in the former case. The results in our work can serve as a paradigmatic starting point for more systematic exploration of the largely uncharted physics of extensive entanglement, both analytical and numerical.
We introduce a novel scheme of quantum recursive programming, in which large unitary transformations, i.e. quantum gates, can be recursively defined using quantum case statements, which are quantum counterparts of conditionals and case statements extensively used in classical programming. A simple programming language for supporting this kind of quantum recursion is defined, and its semantics is formally described. A series of examples are presented to show that some quantum algorithms can be elegantly written as quantum recursive programs.
A quantum optical model for the high-order harmonic generation is presented, in which both the exciting field and the high harmonic modes are quantized, while the target material appears via parameters only. As a consequence, the model is independent from the excited material system to a large extent, and allows us to focus on the properties of the electromagnetic fields. Technically, the Hamiltonian known for parametric down-conversion is adopted, where photons in the $n$th harmonic mode are created in exchange of annihilating $n$ photons from the fundamental mode. In our treatment, initially the fundamental mode is in a coherent state corresponding to large photon numbers, while the high harmonic modes are in vacuum state. Due to the interaction, the latter modes get populated while the fundamental one loses photons. Analytical approximations are presented for the time evolution that are verified by numerically exact calculations. For multimode, finite bandwith excitation, the time dependence of the high-order harmonic radiation is also given.
Neural networks have shown their effectiveness in various tasks in the realm of quantum computing. However, their application in quantum error mitigation, a crucial step towards realizing practical quantum advancements, has been restricted by reliance on noise-free statistics. To tackle this critical challenge, we propose a data augmentation empowered neural model for error mitigation (DAEM). Our model does not require any prior knowledge about the specific noise type and measurement settings and can estimate noise-free statistics solely from the noisy measurement results of the target quantum process, rendering it highly suitable for practical implementation. In numerical experiments, we show the model's superior performance in mitigating various types of noise, including Markovian noise and Non-Markovian noise, compared with previous error mitigation methods. We further demonstrate its versatility by employing the model to mitigate errors in diverse types of quantum processes, including those involving large-scale quantum systems and continuous-variable quantum states. This powerful data augmentation-empowered neural model for error mitigation establishes a solid foundation for realizing more reliable and robust quantum technologies in practical applications.
The coexistence of antiferromagnetic and ferromagnetic order at room temperature in single-phase van der Waals materials, particularly within the two-dimensional limit, has attracted significant research interest. Nonetheless, such materials are rare. In this work, we introduce an itinerant van der Waals antiferromagnet (Fe0.56Co0.44)5GeTe2, where the ferromagnetic order of its exfoliated flakes remains discernible up to room temperature, extending down to the monolayer limit. A notable phenomenon observed is the evident odd-even layer-number effect at high temperature (e.g., T = 150 K). Such behaviour can be expounded by a linear-chain model. Of particular interest is the robust ferromagnetic order observed in even-layer flakes at low temperature (e.g., T = 2 K), which could potentially be attributed to spin-polarized defects. The intricate interplay among magnetic field strength, layer number, and temperature gives rise to a diverse array of phenomena, holding promise not only for new physics but also for practical applications.
We will investigate the $\alpha$-$z$-R\'{e}nyi divergence in the general von Neumann algebra setting based on Haagerup non-commutative $L^p$-spaces. In particular, we establish almost all its expected properties when $0 < \alpha < 1$ and some of them when $\alpha > 1$. In an appendix we also give an equality condition for generalized H\"{o}lder's inequality in Haagerup non-commutative $L^p$-spaces.
The tetron architecture is a promising candidate for topological quantum computation. Each tetron Majorana island has four Majorana zero modes, and possible measurements are constrained to span zero or two Majoranas per tetron. Such measurements are known to be sufficient for correcting so-called "bosonic errors," which affect an even number of Majoranas per tetron. We demonstrate that such measurements are also sufficient for correcting "fermionic errors," which affect an odd number of Majoranas per tetron. In contrast, previous proposals for "fermionic error correction" on tetrons introduce more experimental challenges. We show that "fermionic codes" can be derived from traditional "bosonic codes" by inclusion of tetrons in the stabilizer group.
We study the buildup of antiferromagnetic (AF) correlation in the dynamically tuned Ising models which are realized by the Rydberg atomic system. In short-time scale, we apply Magnus expansion (ME) to derive the high-order analytic expression of the connected correlation functions and compare it with exactly numerical results for the different lattice geometries, e.g., 1D chain, $2 \times n$ lattice, and $n \times n$ lattice. It is shown that the high-order expansion is required to describe accurately the buildup of AF correlation in the quench dynamics. Moreover, through a 2D square lattice, we find that the magnitude of AF correlation for the same Manhattan distance is proportional to the number of the shortest paths in a sufficiently long time until long and distinct paths are involved significantly with the buildup of the correlation. Finally, we propose an applicable experimental setup to realize our findings.
Classically, the edit distance of two length-$n$ strings can be computed in $O(n^2)$ time, whereas an $O(n^{2-\epsilon})$-time procedure would falsify the Orthogonal Vectors Hypothesis. If the edit distance does not exceed $k$, the running time can be improved to $O(n+k^2)$, which is near-optimal (conditioned on OVH) as a function of $n$ and $k$. Our first main contribution is a quantum $\tilde{O}(\sqrt{nk}+k^2)$-time algorithm that uses $\tilde{O}(\sqrt{nk})$ queries, where $\tilde{O}(\cdot)$ hides polylogarithmic factors. This query complexity is unconditionally optimal, and any significant improvement in the time complexity would resolve a long-standing open question of whether edit distance admits an $O(n^{2-\epsilon})$-time quantum algorithm. Our divide-and-conquer quantum algorithm reduces the edit distance problem to a case where the strings have small Lempel-Ziv factorizations. Then, it combines a quantum LZ compression algorithm with a classical edit-distance subroutine for compressed strings. The LZ factorization problem can be classically solved in $O(n)$ time, which is unconditionally optimal in the quantum setting. We can, however, hope for a quantum speedup if we parameterize the complexity in terms of the factorization size $z$. Already a generic oracle identification algorithm yields the optimal query complexity of $\tilde{O}(\sqrt{nz})$ at the price of exponential running time. Our second main contribution is a quantum algorithm that achieves the optimal time complexity of $\tilde{O}(\sqrt{nz})$. The key tool is a novel LZ-like factorization of size $O(z\log^2n)$ whose subsequent factors can be efficiently computed through a combination of classical and quantum techniques. We can then obtain the string's run-length encoded Burrows-Wheeler Transform (BWT), construct the $r$-index, and solve many fundamental string processing problems in time $\tilde{O}(\sqrt{nz})$.
Amplification (mitigation) is the increase (decrease) in the change of thermodynamic quantities when an initial thermal state is thermalized to a different temperature in the presence of constraints, studied thus far only for permutationally invariant baths. In this manuscript, we generalize amplification and mitigation to accommodate generic strong symmetries of open quantum systems and connect the phenomenon to Landauer's erasure. We exemplify our general theory with a new bath-induced battery charging protocol that overcomes the passivity of KMS-preserving transitions.
Recollision processes are fundamental to strong-field physics and attoscience, thus models connecting recolliding trajectories to quantum amplitudes are a crucial part in furthering understanding of these processes. We report developments in the semiclassical path-integral-based Coulomb quantum-orbit strong-field approximation model for strong-field ionization by including an additional phase known as Maslov's phase and implementing a new solution strategy via Monte-Carlo-style sampling of the initial momenta. In doing so, we obtain exceptional agreement with solutions to the time-dependent Schr\"odinger equation for hydrogen, helium, and argon. We provide an in-depth analysis of the resulting photoelectron momentum distributions for these targets, facilitated by the quantum-orbits arising from the solutions to the saddle-point equations. The analysis yields a new class of rescattered trajectories that includes the well-known laser-driven long and short trajectories, along with novel Coulomb-driven rescattered trajectories. By virtue of the precision of the model, it opens the door to detailed investigations of a plethora of strong-field phenomena such as photoelectron holography, laser-induced electron diffraction and high-order above threshold ionization.
A strategy for the analysis of active debris removal missions targeting multiple objects from a set of objects in near-circular orbit with similar inclination is presented. Algebraic techniques successfully reduce the orbital mechanics regarding specific inter-debris transfer and disposal methods to simple computations, which can be used as the coefficients of a quadratic unconstrained binary optimisation (QUBO) problem formulation which minimises the total propellant used in the mission whilst allowing for servicing time and meeting the mission deadline. The QUBO is validated by solving artificial small problems (from 2 to 11 debris) using classical computational methods and the weaknesses in using these methods are examined prior to solution using quantum annealing hardware. The quantum processing unit (QPU) and quantum-classical hybrid solvers provided by D-Wave are then used to solve the same small problems, with attention paid to evident strengths and weaknesses of each approach. Hybrid solvers are found to be significantly more effective at solving larger problems. Finally, the hybrid method is used to solve a large problem using a real dataset. From a set of 79 debris objects resulting from the destruction of the Kosmos-1408 satellite, an active debris removal mission starting on 30 September 2023 targeting 5 debris objects for disposal within a year with 20 days servicing time per object is successfully planned. This plan calculates the total propellant cost of transfer and disposal to be 0.87km/s and would be complete well within the deadline at 241 days from the start date. This problem uses 6,478 binary variables in total and is solved using around 25s of QPU access time.
We introduce a Hilbert space based resource theory of Bell nonlocality with the aim of providing bona fide measures of quantum nonlocality depending only on the intrinsic properties of the quantum states being considered. We construct our theory by defining the set of local (or free) states, i.e., the states that do not violate the Clauser-Horne-Shimony-Holt inequality; the set of free operations, i.e., the transformations that do not create the nonlocality resource, which includes local operations and shared randomness; and suitable measures of nonlocality based either on geometric distances or relative entropies with respect to the set of local states. We discuss the basic axiomatic structure that is needed for a meaningful characterization and quantification of Bell nonlocality and we illustrate the general resource theory so developed by applying it to specific classes of quantum states, including two-qubit Werner states, Bell-diagonal states, and Bell-diagonal states at fixed convexity.
Measure theory is used in physics, not just to capture classical probability, but also to quantify the number of states. In previous works, we found that state quantification plays a foundational role in classical mechanics, and therefore, we set ourselves to construct the quantum equivalent of the Liouville measure. Unlike the classical counterpart, this quantized measure is non-additive and has a unitary lower bound (i.e. no set of states can have less than one state). Conversely, requiring that state quantification is finite for finite continuous regions and that each state counts as one already implies non-additivity, which in turn implies the failure of classical theory. In this article we show these preliminary results and outline a new line of inquiry that may provide a different insight into the foundations of quantum theory. Additionally, this new approach may prove to be useful to those interested in a quantized theory of space-time, as we believe this requires a quantized measure for the quantification of the independent degrees of freedom.
In this manuscript, we investigate the enhancement of the transfer of quantum correlations from squeezed light to movable mirrors within an optomechanical system. This enhancement was achieved via the injection of squeezed light in the cavities and via intracavity squeezed light. We quantify the entanglement between mechanical oscillators via logarithmic negativity. We demonstrate that entanglement is influenced by various factors, including the gain of the parametric amplifier, the squeezing parameter characterizing the squeezed light, the rate of the phonon tunneling process, the coupling strength of the photon hopping process and the bath temperature of the mechanical oscillators. We have shown that entanglement can be improved by a convenient choice of coupling strength in the case of the photon hopping process, as well as for specified values of the gain of the parametric amplifier.
Quantum illumination uses quantum correlations to enhance the detection of an object in the presence of background noise. This advantage has been shown to exist even if one uses non-optimal direct measurements on the two correlated modes. Here we present a protocol that mimics the behaviour of quantum illumination, but does not use correlated or entangled modes. Instead, the protocol uses coherent (or phase-randomized coherent) pulses with randomly chosen intensities. The intensities are drawn from a distribution such that the average state looks thermal. Under appropriate conditions, the mimic protocol can perform similarly to quantum illumination schemes that use direct measurements. This holds even for a reflectance as low as $10^{-7}$. We also present an analytic condition which allows one to determine the sets of parameters in which each protocol works best.
Quantum effects in photosynthetic energy transport in nature, especially for the typical Fenna-Matthews-Olson (FMO) complexes, are extensively studied in quantum biology. Such energy transport processes can be investigated as open quantum systems that blend the quantum coherence and environmental noises, and have been experimentally simulated on a few quantum devices. However, the existing experiments always lack a solid quantum simulation for the FMO energy transport due to their constraints to map a variety of issues in actual FMO complexes that have rich biological meanings. Here we successfully map the full coupling profile of the seven-site FMO structure by comprehensive characterization and precise control of the evanescent coupling of the three-dimensional waveguide array. By applying a stochastic dynamical modulation on each waveguide, we introduce the base site energy and the dephasing term in colored noises to faithfully simulate the power spectral density of the FMO complexes. We show our photonic model well interprets the issues including the reorganization energy, vibrational assistance, exciton transfer and energy localization. We further experimentally demonstrate the existence of an optimal transport efficiency at certain dephasing strength, providing a window to closely investigate environment-assisted quantum transport.
We've studied the B800 part of Rhodoblastus acidophilus light-harvesting complex (LH2) by several quantum chemical techniques based on the density functional theory (DFT) and determined the specific method and a minimal reliable model suitable for further studies of the LH2. In addition to bacteriochlorophyll a molecules, the minimal model includes two $\alpha$ and one $\beta$ chain amino acids. Within the model, we are able to reproduce the contribution of the B800 ring of nine bacteriochlorophyll a molecules to the near infrared $Q_y$ absorption band. We also discuss the use of hybrid DFT calculations for precise energy and optical estimations and DFT-based tight binding (DFTB) method for the large-scale calculations. Crucial importance of Hartree-Fock exchange interaction for the correct description of B800 peak position was shown.
We study the quantum squeezing produced in self-induced transparency in a photonic crystal fiber by performing a fully quantum simulation based on the positive $P$ representation. The amplitude squeezing depends on the area of the initial pulse: when the area is $2\pi$, there is no energy absorption and no amplitude squeezing. However, when the area is between 2$\pi$ and 3$\pi$, one observes amplitude-dependent energy absorption and a significant amount of squeezing. We also investigate the effect of damping and temperature: the results indicate that a heightened atom-pulse coupling, caused by an increase in the spontaneous emission ratio reduces the amplitude squeezing.
Quantum computing has recently emerged as a transformative technology. Yet, its promised advantages rely on efficiently translating quantum operations into viable physical realizations. In this work, we use generative machine learning models, specifically denoising diffusion models (DMs), to facilitate this transformation. Leveraging text-conditioning, we steer the model to produce desired quantum operations within gate-based quantum circuits. Notably, DMs allow to sidestep during training the exponential overhead inherent in the classical simulation of quantum dynamics -- a consistent bottleneck in preceding ML techniques. We demonstrate the model's capabilities across two tasks: entanglement generation and unitary compilation. The model excels at generating new circuits and supports typical DM extensions such as masking and editing to, for instance, align the circuit generation to the constraints of the targeted quantum device. Given their flexibility and generalization abilities, we envision DMs as pivotal in quantum circuit synthesis, enhancing both practical applications but also insights into theoretical quantum computation.
As with a Bell inequality, Hardy's paradox manifests a contradiction between the prediction given by quantum theory and local-hidden variable theories. In this work, we give two generalizations of Hardy's arguments for manifesting such a paradox to an arbitrary but symmetric Bell scenario involving two observers. Our constructions recover that of Meng et al. [Phys. Rev. A. 98, 062103 (2018)] and that first discussed by Cabello [Phys. Rev. A 65, 032108 (2002)] as special cases. Among the two constructions, one can be naturally interpreted as a demonstration of the failure of the transitivity of implications (FTI). Moreover, a special case of which is equivalent to a ladder-proof-type argument for Hardy's paradox. Through a suitably generalized notion of success probability called degree of success, we provide evidence showing that the FTI-based formulation exhibits a higher degree of success compared with all other existing proposals. Moreover, this advantage seems to persist even if we allow imperfections in realizing the zero-probability constraints in such paradoxes. Explicit quantum strategies realizing several of these proofs of nonlocality without inequalities are provided.
Time-bin encoding has been widely used for implementing quantum key distribution (QKD) on optical fiber channels due to its robustness with respect to drifts introduced by the optical fiber. However, due to the use of interferometric structures, achieving stable and low intrinsic Quantum Bit Error rate (QBER) in time-bin systems can be challenging. A key device for decoy-state prepare & measure QKD is represented by the state encoder, that must generate low-error and stable states with different values of mean photon number. Here we propose the MacZac (Mach-Zehder-Sagnac), a time-bin encoder with ultra-low intrinsic QBER (<2e-5) and high stability. The device is based on nested Sagnac and Mach-Zehnder interferometers and uses a single phase modulator for both decoy and state preparation, greatly simplifying the optical setup. The encoder does not require any active compensation or feedback system and it can be scaled for the generation of states with arbitrary dimension. We experimentally realized and tested the device performances as a stand alone component and in a complete QKD experiments. Thanks to the capacity to combine extremely low QBER, high stability and experimental simplicity the proposed device can be used as a key building block for future high-performance, low-cost QKD systems.
The asymptotic quantum trajectory of weak continuous measurement for the magnetometer is investigated. The magnetometer refers to a setup where the field-to-estimate and the measured moment are orthogonal, and the quantum state is governed by the stochastic master equation which, in addition to a deterministic part, depends on the measurement outcomes. We find that the asymptotic behavior is insensitive to the initial state in the following sense: given one realization, the quantum trajectories starting from arbitrary initial states asymptotically converge to the {\em same} realization-specific {\em pure} state. For single-qubit systems, we are able to prove this statement within the framework of Probability Theory by deriving and analyzing an effective one-dimensional stochastic equation. Numerical simulations strongly indicate that the same statement holds for multi-qubit systems. Built upon this conclusion, we consider the problem of real-time parameter estimation whose feasibility hinges on the insensitivity to the initial state, and explicitly propose and test a scheme where the quantum state and the field-to-estimate are updated simultaneously.
Cold atomic gases have become a paradigmatic system for exploring fundamental physics, which at the same time allows for applications in quantum technologies. The accelerating developments in the field have led to a highly advanced set of engineering techniques that, for example, can tune interactions, shape the external geometry, select among a large set of atomic species with different properties, or control the number of atoms. In particular, it is possible to operate in lower dimensions and drive atomic systems into the strongly correlated regime. In this review, we discuss recent advances in few-body cold atom systems confined in low dimensions from a theoretical viewpoint. We mainly focus on bosonic systems in one dimension and provide an introduction to the static properties before we review the state-of-the-art research into quantum dynamical processes stimulated by the presence of correlations. Besides discussing the fundamental physical phenomena arising in these systems, we also provide an overview of the calculational and numerical tools and methods that are commonly used, thus delivering a balanced and comprehensive overview of the field. We conclude by giving an outlook on possible future directions that are interesting to explore in these correlated systems.
This work provides a relativistic, digital quantum simulation scheme for both $2+1$ and $3+1$ dimensional quantum electrodynamics (QED), based on a discrete spacetime formulation of theory. It takes the form of a quantum circuit, infinitely repeating across space and time, parametrised by the discretization step $\Delta_t=\Delta_x$. Strict causality \PA{at each step} is ensured as circuit wires coincide with the lightlike worldlines of QED; simulation time under decoherence is optimized. The construction replays the logic that leads to the QED Lagrangian. Namely, it starts from the Dirac quantum walk, well-known to converge towards free relativistic fermions. It then extends the quantum walk into a multi-particle sector quantum cellular automata in a way which respects the fermionic anti-commutation relations and the discrete gauge invariance symmetry. Both requirements can only be achieved at cost of introducing the gauge field. Lastly the gauge field is given its own electromagnetic dynamics, which can be formulated as a quantum walk at each plaquette.
Reconstructing the state of many-body quantum systems is of fundamental importance in quantum information tasks, but extremely challenging due to the curse of dimensionality. In this work, we present an efficient quantum tomography approach that unifies the state factored and projected methods to tackle the rank-deficient issue and incorporates a momentum-accelerated Rprop gradient algorithm to speed up the optimization process. In particular, the techniques of state factorization and P-order absolute map are jointly introduced to ensure both the positivity and rank of state matrices learned in the maximum likelihood function. Further, the proposed state-mapping method can substantially improve the tomography accuracy of other QST algorithms. Finally, numerical experiments demonstrate that the unified strategy is able to tackle the rank-deficient problem and admit a faster convergence and excellent purity robustness. We find that our method can accomplish the task of full tomography of random 11-qubit mixed states within one minute.
It is important to find feasible measurement bounds for quantum information protocols. We present analytic bounds for quantum illumination with Gaussian states when using an on-off detection or a photon number resolving (PNR) detection, where its performance is evaluated with signal-to-noise ratio. First, for coincidence counting measurement, the best performance is given by the two-mode squeezed vacuum (TMSV) state which outperforms the coherent state and the classically correlated thermal (CCT) state. However, the coherent state can beat the TMSV state with increasing signal mean photon number in the case of the on-off detection. Second, the performance is enhanced by taking Fisher information approach of all counting probabilities including non-detection events. In the Fisher information approach, the TMSV state still presents the best performance but the CCT state can beat the TMSV state with increasing signal mean photon number in the case of the on-off detection. Furthermore, we show that it is useful to take the PNR detection on the signal mode and the on-off detection on the idler mode, which reaches similar performance of using PNR detections on both modes.
We propose a nonvariational scheme for geometry optimization of molecules for the first-quantized eigensolver, a recently proposed framework for quantum chemistry using the probabilistic imaginary-time evolution (PITE) on a quantum computer. While the electrons in a molecule are treated in the scheme as quantum mechanical particles, the nuclei are treated as classical point charges. We encode both electronic states and candidate molecular geometries as a superposition of many-qubit states, leading to quantum advantage. The histogram formed by outcomes of repeated measurements gives the global minimum of the energy surface. We demonstrate that the circuit depth scales as O (n_e^2 poly(log n_e)) for the electron number n_e, which can be reduced to O (n_e poly(log n_e)) if extra O (n_e log n_e) qubits are available. We corroborate the scheme via numerical simulations. The new efficient scheme will be helpful for achieving scalability of practical quantum chemistry on quantum computers. As a special case of the scheme, a classical system composed only of charged particles is admitted. We also examine the scheme adapted to variational calculations that prioritize saving circuit depths for noisy intermediate-scale quantum (NISQ) devices.
Quantum search algorithms offer a remarkable advantage of quadratic reduction in query complexity using quantum superposition principle. However, how an actual architecture may access and handle the database in a quantum superposed state has been largely unexplored so far; the quantum state of data was simply assumed to be prepared and accessed by a black-box operation -- so-called oracle, even though this process, if not appropriately designed, may adversely diminish the quantum query advantage. Here, we introduce an efficient quantum data-access process, dubbed as quantum data-access machine (QDAM), and present a general architecture for quantum search algorithm. We analyze the runtime of our algorithm in view of the fault-tolerant quantum computation (FTQC) consisting of logical qubits within an effective quantum error correction code. Specifically, we introduce a measure involving two computational complexities, i.e. quantum query and $T$-depth complexities, which can be critical to assess performance since the logical non-Clifford gates, such as the $T$ (i.e., $\pi/8$ rotation) gate, are known to be costliest to implement in FTQC. Our analysis shows that for $N$ searching data, a QDAM model exhibiting a logarithmic, i.e., $O(\log{N})$, growth of the $T$-depth complexity can be constructed. Further analysis reveals that our QDAM-embedded quantum search requires $O(\sqrt{N} \times \log{N})$ runtime cost. Our study thus demonstrates that the quantum data search algorithm can truly speed up over classical approaches with the logarithmic $T$-depth QDAM as a key component.
A neural network is a powerful tool that can uncover hidden laws beyond human intuition. However, it often appears as a black box due to its complicated nonlinear structures. By drawing upon the Gutzwiller mean-field theory, we can showcase a principle of sign rules for ordered states in qubit lattice models. We introduce a shallow feed-forward neural network with a single hidden neuron to present these sign rules. We conduct systematical benchmarks in various models, including the generalized Ising, spin-$1/2$ XY, (frustrated) Heisenberg rings, triangular XY antiferromagnet on a torus, and the Fermi-Hubbard ring at an arbitrary filling. These benchmarks show that all the leading-order sign rule characteristics can be visualized in classical forms, such as pitch angles. Besides, quantum fluctuations can result in an imperfect accuracy rate quantitatively.
We develop the theory of quantum (a.k.a. noncommutative) relations and quantum (a.k.a. noncommutative) graphs in the finite-dimensional covariant setting, where all systems (finite-dimensional $C^*$-algebras) carry an action of a compact quantum group $G$, and all channels (completely positive maps preserving the canonical $G$-invariant state) are covariant with respect to the $G$-actions. We motivate our definitions by applications to zero-error quantum communication theory with a symmetry constraint. Some key results are the following: 1) We give a necessary and sufficient condition for a covariant quantum relation to be the underlying relation of a covariant channel. 2) We show that every quantum confusability graph with a $G$-action (which we call a quantum $G$-graph) arises as the confusability graph of a covariant channel. 3) We show that a covariant channel is reversible precisely when its confusability $G$-graph is discrete. 4) When $G$ is quasitriangular (this includes all compact groups), we show that covariant zero-error source-channel coding schemes are classified by covariant homomorphisms between confusability $G$-graphs.
Hardy's argument constitutes an elegant proof of quantum nonlocality. In this work, we report an exotic application of Hardy's nonlocal correlations in two-party communication setup. We come up with a task, wherein a positive payoff can be through an $1$ bit of communication from the sender to the receiver if and only if the communication channel is assisted with a no-signaling correlation exhibiting Hardy's nonlocality. This further prompts us to establish a counter-intuitive result in correlation assisted reverse zero-error channel coding scenario, where the aim is to simulate a higher input-output noisy classical channel by a lower input-output noiseless one in assistance with pre-shared correlations. We show that there exist such reverse zero-error channel simulation tasks where non-maximally entangled states are preferable over the assistance with a maximally entangled state, even when the former states carry an arbitrarily small amount of entanglement. Our work thus establishes that within the operational paradigm of local operations and limited classical communication the structure of entangled resources is even more complex to characterize.
We study a generalization of a recently introduced Dicke trimer model [Phys. Rev. Lett. 128, 163601, Phys. Rev. Research 5, L042016], which allows for cavity losses and unbalanced light-matter interactions (in which rotating and counter-rotating terms can be tuned independently). We find that in the extreme unbalanced limit, the $U(1)$ symmetry of the Tavis-Cummings model is restored, qualitatively altering the critical phenomena in the superradiant phase due to the presence of a zero-energy mode. To analyze this general regime, we develop a semiclassical theory based on a re-quantization technique. This theory also provides further physical insight on a recently reported anomalous finite critical fluctuations in the time-reversal broken regime. Moving to the open-Dicke case, by introducing local dissipation to the cavities, we observe the emergence of a rich range of nonequilibrium phases characterized by trivial and non-trivial dynamical signatures. In the former case, we identify, when time-reversal symmetry is present, a new stationary phase that features superradiant states in two of the three cavities and a normal state in the other cavity. In the latter case, we observe the emergence of dynamical phases in which the system exhibits superradiant oscillations, characterized by periodic or chaotic phase space patterns. The landscape of transitions associated with these dynamical phases features a wide range of qualitatively different behaviours such as Hopf bifurcations, anomalous Hopf bifurcations, collisions between basins of attraction, and exterior crises. We highlight how the two-critical-scalings feature of the closed model is robust under dissipation while the phenomenon of anomalous finite critical fluctuations becomes a mean-field scaling in the open model.
Optical dipole micro-traps for atoms based on constructive superposition of two-colour evanescent light waves, formed by corresponding optical modes of two crossed suspended photonic rib waveguides, are modelled. The main parameters of the traps for rubidium atoms, such as potential depth, tunnelling rates of atoms from the trap and coherence time of the trapped atoms are estimated. Applications of such traps for quantum memory and quantum logic devices are discussed.
Quantum metrology protocols using entangled states of large spin ensembles attempt to achieve measurement sensitivities surpassing the standard quantum limit (SQL), but in many cases they are severely limited by even small amounts of technical noise associated with imperfect sensor readout. Amplification strategies based on time-reversed coherent spin-squeezing dynamics have been devised to mitigate this issue, but are unfortunately very sensitive to dissipation, requiring a large single-spin cooperativity to be effective. Here, we propose a new dissipative protocol that combines amplification and squeezed fluctuations. It enables the use of entangled spin states for sensing well beyond the SQL even in the presence of significant readout noise. Further, it has a strong resilience against undesired single-spin dissipation, requiring only a large collective cooperativity to be effective.
The implementation of a superradiant laser as an active frequency standard is predicted to provide better short-term stability and robustness to thermal and mechanical fluctuations when compared to standard passive optical clocks. However, despite significant recent progress, the experimental realization of continuous wave superradiant lasing still remains an open challenge as it requires continuous loading, cooling, and pumping of active atoms within an optical resonator. Here we propose a new scenario for creating continuous gain by using optical forces acting on the states of a two-level atom via bichromatic coherent pumping of a cold atomic gas trapped inside a single-mode cavity. Analogous to atomic maser setups, tailored state-dependent forces are used to gather and concentrate excited-state atoms in regions of strong atom-cavity coupling while ground-state atoms are repelled. To facilitate numerical simulations of a sufficiently large atomic ensemble, we rely on a second-order cumulant expansion and describe the atomic motion in a semi-classical point-particle approximation subject to position-dependent light shifts which induce optical gradient forces along the cavity axis. We study minimal conditions on pump laser intensities and detunings required for collective superradiant emission. Balancing Doppler cooling and gain-induced heating we identify a parameter regime of a continuous narrow-band laser operation close to the bare atomic frequency.
Transferring quantum information between different types of quantum hardware is crucial for integrated quantum technology. In particular, converting information between continuous-variable (CV) and discrete-variable (DV) devices enables many applications in quantum networking, quantum sensing, quantum machine learning, and quantum computing. This paper addresses the transfer of CV-encoded information between CV and DV devices. We present a resource-efficient method for encoding CV states and implementing CV gates on DV devices, as well as two measurement-based protocols for transferring CV states between CV and DV devices. The success probability of the transfer protocols depends on the measurement outcome and can be increased to near-deterministic values by adding ancillary qubits to the DV devices.
We study classical shadows protocols based on randomized measurements in $n$-qubit entangled bases, generalizing the random Pauli measurement protocol ($n = 1$). We show that entangled measurements ($n\geq 2$) enable nontrivial and potentially advantageous trade-offs in the sample complexity of learning Pauli expectation values. This is sharply illustrated by shadows based on two-qubit Bell measurements: the scaling of sample complexity with Pauli weight $k$ improves quadratically (from $\sim 3^k$ down to $\sim 3^{k/2}$) for many operators, while others become impossible to learn. Tuning the amount of entanglement in the measurement bases defines a family of protocols that interpolate between Pauli and Bell shadows, retaining some of the benefits of both. For large $n$, we show that randomized measurements in $n$-qubit GHZ bases further improve the best scaling to $\sim (3/2)^k$, albeit on an increasingly restricted set of operators. Despite their simplicity and lower hardware requirements, these protocols can match or outperform recently-introduced "shallow shadows" in some practically-relevant Pauli estimation tasks.
Building a quantum internet requires efficient and reliable quantum hardware, from photonic sources to quantum repeaters and detectors, ideally operating at telecommunication wavelengths. Thanks to their high brightness and single-photon purity, quantum dot (QD) sources hold the promise to achieve high communication rates for quantum-secured network applications. Furthermore, it was recently shown that excitation schemes, such as longitudinal acoustic phonon-assisted (LA) pumping, provide security benefits by scrambling the coherence between the emitted photon-number states. In this work, we investigate further advantages of LA-pumped quantum dots with emission in the telecom C-band as a core hardware component of the quantum internet. We experimentally demonstrate how varying the pump energy and spectral detuning with respect to the excitonic transition can improve quantum-secured communication rates and provide stable emission statistics regardless of network-environment fluctuations. These findings have significant implications for general implementations of QD single-photon sources in practical quantum communication networks.
Consider a general quantum source that emits at discrete time steps quantum pure states which are chosen from a finite alphabet according to some probability distribution which may depend on the whole history. Also, fix two positive integers $m$ and $l$. We encode any tensor product of $ml$ many states emitted by the quantum source by breaking it into $m$ many blocks where each block has length $l$, and considering sequences of $m$ many isometries so that each isometry encodes one of these blocks into the Fock space, followed by the concatenation of their images. We only consider certain sequences of such isometries that we call "special block codes" in order to ensure that the the string of encoded states is uniquely decodable. We compute the minimum average codeword length of these encodings which depends on the quantum source and the integers $m$, $l$, among all possible special block codes. Our result extends the result of [Bellomo, Bosyk, Holik and Zozor, Scientific Reports 7.1 (2017): 14765] where the minimum was computed for one block, i.e. for $m=1$.
Dynamical generation of strong and scalable quantum resources, like many-body entanglement and Bell correlations, in spin-$1/2$ chains, is possible with all-to-all interactions, either for constant interaction strength realizing one-axis twisting protocol or for power-law decaying potentials. We show, however, that such quantum resources can also be dynamically generated with a finite range of interactions. We identify a necessary critical range and indicate a critical time when scalable quantum correlations appear. Finally, we show that the certification of generated states is accessible in the modern quantum simulator platforms.
Quantum incompatibility is referred as the phenomenon that some quantum measurements cannot be performed simultaneously, and is also used in various quantum information tasks. However, it is still a challenge to certify whether a given set of multiple high-dimensional measurements respects a specific structure of incompatibility. To address this problem, we propose a modified quantum state discrimination protocol that decomposes complex compatibility structures into pair-wise ones and employs noise robustness to witness incompatibility structures. Our method is capable of detecting genuine $n$-wise incompatibility and some specific general compatibility structures, as demonstrated by our experimental verification of incompatibility structures of $4$ mutually unbiased bases in a qutrit system. The experimental results show that our approach is able to witness incompatibility structures, i.e., the hierarchy of quantum incompatibility resources.
In contrast to interferometry-based quantum sensing, where interparticle interaction is detrimental, quantum many-body probes exploit such interactions to achieve quantum-enhanced sensitivity. In most of the studied quantum many-body probes, the interaction is considered to be short-ranged. Here, we investigate the impact of long-range interaction at various filling factors on the performance of Stark quantum probes for measuring a small gradient field. These probes harness the ground state Stark localization phase transition which happens at an infinitesimal gradient field as the system size increases. Our results show that while super-Heisenberg precision is always achievable in all ranges of interaction, the long-range interacting Stark probe reveals two distinct behaviors. First, by algebraically increasing the range of interaction, the localization power enhances and thus the sensitivity of the probe decreases. Second, as the interaction range becomes close to a fully connected graph its effective localization power disappears and thus the sensitivity of the probe starts to enhance again. The super-Heisenberg precision is achievable throughout the extended phase until the transition point and remains valid even when the state preparation time is incorporated in the resource analysis. As the probe enters the localized phase, the sensitivity decreases and its performance becomes size-independent, following a universal behavior. In addition, our analysis shows that lower filling factors lead to better precision for measuring weak gradient fields.
Current noisy intermediate-scale quantum (NISQ) trapped-ion devices are subject to errors which can significantly impact the accuracy of calculations if left unchecked. A form of error mitigation called zero noise extrapolation (ZNE) can decrease an algorithm's sensitivity to these errors without increasing the number of required qubits. Here, we explore different methods for integrating this error mitigation technique into the Variational Quantum Eigensolver (VQE) algorithm for calculating the ground state of the HeH+ molecule at 0.8 Angstrom in the presence of realistic noise. Using the Quantum Scientific Computing Open User Testbed (QSCOUT) trapped-ion device, we test three methods of scaling noise for extrapolation: time-stretching the two-qubit gates, scaling the sideband amplitude parameter, and inserting two-qubit gate identity operations into the ansatz circuit. We find time-stretching and sideband amplitude scaling fail to scale the noise on our particular hardware in a way that can be directly extrapolated to zero noise. Scaling our noise with global gate identity insertions and extrapolating after variational optimization, we achieve an estimate of the ground state energy within -0.004 +- 0.04 Hartree; outside chemical accuracy, but greatly improved over our non-error-mitigated estimate with error 0.127 +- 0.008 Hartree. Our results show that the efficacy of this error mitigation technique depends on choosing the correct implementation for a given device architecture.
Tensor networks capture large classes of ground states of phases of quantum matter faithfully and efficiently. Their manipulation and contraction has remained a challenge over the years, however. For most of the history, ground state simulations of two-dimensional quantum lattice systems using (infinite) projected entangled pair states have relied on what is called a time-evolving block decimation. In recent years, multiple proposals for the variational optimization of the quantum state have been put forward, overcoming accuracy and convergence problems of previously known methods. The incorporation of automatic differentiation in tensor networks algorithms has ultimately enabled a new, flexible way for variational simulation of ground states and excited states. In this work, we review the state of the art of the variational iPEPS framework. We present and explain the functioning of an efficient, comprehensive and general tensor network library for the simulation of infinite two-dimensional systems using iPEPS, with support for flexible unit cells and different lattice geometries.
We study the ground-state correlations between two atoms in a two-dimensional isotropic harmonic trap. We consider a finite-range soft-core interaction that can be applied to simulate various atomic systems. We provide detailed results on the dependence of the correlations on the parameters of the system. Our investigations show that in the hardcore limit, the wave function can be approximated as the product of the radial and angular components regardless of the interaction range. This implies that the radial and angular correlations are independent of one another. However, correlations within the radial and angular components persist and are heavily influenced by the interaction range. The radial correlations are generally weaker than the angular correlations. When soft-core interactions are considered, the correlations exhibit more complex behavior.
Memory is an indispensable component in classical computing systems. While the development of quantum computing is still in its early stages, current quantum processing units mainly function as quantum registers. Consequently, the actual role of quantum memory in future advanced quantum computing architectures remains unclear. With the rapid scaling of qubits, it is opportune to explore the potential and feasibility of quantum memory across different substrate device technologies and application scenarios. In this paper, we provide a full design stack view of quantum memory. We start from the elementary component of a quantum memory device, quantum memory cells. We provide an abstraction to a quantum memory cell and define metrics to measure the performance of physical platforms. Combined with addressing functionality, we then review two types of quantum memory devices: random access quantum memory (RAQM) and quantum random access memory (QRAM). Building on top of these devices, quantum memory units in the computing architecture, including building a quantum memory unit, quantum cache, quantum buffer, and using QRAM for the quantum input-output module, are discussed. We further propose the programming model for the quantum memory units and discuss their possible applications. By presenting this work, we aim to attract more researchers from both the Quantum Information Science (QIS) and classical memory communities to enter this emerging and exciting area.
Solid-state magnetic resonance is a unique technique that can reveal the dynamics of complex biological systems with atomic resolution. Longitudinal relaxation is a mechanism that returns longitudinal nuclear magnetization to its thermal equilibrium by incoherent processes. The measured longitudinal relaxation rate constant however represents the combination of both incoherent and coherent contributions to the change of nuclear magnetization. This work demonstrates the effect of magic angle spinning rate on the longitudinal relaxation rate constant in two model compounds: L-histidine hydrochloride monohydrate and glycine serving as proxies for isotopically-enriched biological materials. Most notably, it is demonstrated that the longitudinal 15N relaxation of the two nitrogen nuclei in the imidazole ring in histidine is reduced by almost three orders of magnitude at the condition of rotational resonance with the amine, while the amine relaxation rate constant is increased at these conditions. The observed phenomenon may have radical implications for the solid-state magnetic resonance in biophysics and materials, especially in the proper measurement of dynamics and as a selective serial transfer step in dynamic nuclear polarization.
We present a new characterization for the $n$-distillability of Werner states and classify some of them according to their 2-distillability. This result brings out new inequalities with respect to partial traces with bound on the dimension of the system and also the rank of the matrix. For an $n$-partite system we prove that there are $2^n-1$ partial trace inequalities using the dimension of the systems, and for the bounds with respect to the rank, for the case $n=2$ we prove $$\Vert tr_1 C \Vert_2^2+ \Vert tr_2 C \Vert_2^2\leq r \Vert C \Vert_2^2+\frac{1}{r}\vert tr C \vert^2$$ for matrices, which can be written as a rank 1 plus a normal matrix, and $$\left\vert \Vert tr_1 C \Vert_2^2- \Vert tr_2 C \Vert_2^2 \right\vert \leq r \Vert C \Vert_2^2-\frac{1}{r}\vert tr C \vert^2 $$ for any matrix. Here we also present the proofs for many other inequalities in bipartite systems, and for tripartite systems we also obtain some results for positive matrices. Finally, we show numerical results indicating that this results could also be generalized to more families of inequalities depending on more parameters, such as the norm or exponents.
We propose a protocol for the scalable quantum simulation of SU($N$)$\times$U(1) lattice gauge theories with alkaline-earth like atoms in optical lattices in both one- and two-dimensional systems. The protocol exploits the combination of naturally occurring SU($N$) pseudo-spin symmetry and strong inter-orbital interactions that is unique to such atomic species. A detailed ab initio study of the microscopic dynamics shows how gauge invariance emerges in an accessible parameter regime, and allows us to identify the main challenges in the simulation of such theories. We provide quantitative results about the requirements in terms of experimental stability in relation to observing gauge invariant dynamics, a key element for a deeper analysis on the functioning of such class of theories in both quantum simulators and computers.
We proposed a general quantum-computing-based algorithm that harnesses the exponential power of noisy intermediate-scale quantum (NISQ) devices in solving partial differential equations (PDE). This variational quantum eigensolver (VQE)-inspired approach transcends previous idealized model demonstrations constrained by strict and simplistic boundary conditions. It enables the imposition of arbitrary boundary conditions, significantly expanding its potential and adaptability for real-world applications, achieving this "from ad-hoc to systematic" concept. We have implemented this method using the fourth-order PDE (the Euler-Bernoulli beam) as example and showcased its effectiveness with four different boundary conditions. This framework enables expectation evaluations independent of problem size, harnessing the exponentially growing state space inherent in quantum computing, resulting in exceptional scalability. This method paves the way for applying quantum computing to practical engineering applications.
The problem of extending the insights and techniques of categorical quantum mechanics to infinite-dimensional systems was considered in (Coecke and Heunen, 2016). In that work the $\mathrm{CP}^{\infty}$-construction, which recovers the category of Hilbert spaces and quantum operations from the category of Hilbert spaces and bounded linear maps, was defined. Here we show that by a `horizontal categorification' of the $\mathrm{CP}^{\infty}$-construction, one can recover the category of all von Neumann algebras and channels (normal unital completely positive maps) from the 2-category $[W^*]$ of von Neumann algebras, bimodules and intertwiners. As an application, we extend Choi's characterisation of extremal channels between finite-dimensional matrix algebras to a characterisation of extremal channels between arbitrary von Neumann algebras.
Molecules have vibrational, rotational, spin-orbit and hyperfine degrees of freedom, each of which responds in a unique fashion to external electromagnetic radiation. The coherent control over superpositions of these quantum states is key to manipulation of molecules. For example, the better the coherence time the longer quantum simulations can last. The important quantity for controlling a molecule with laser light is its complex-valued molecular dynamic polarizability. Its real part determines the tweezer potential as felt by the molecule, while its imaginary part contributes to the coherence time. Our studies show that efficient trapping of a molecule in an optical potential can be achieved by a selecting laser frequency that has a small detuning (on the order of tens of GHz) relative to an electric-dipole-forbidden molecular transition. Close proximity to this transition allows us to significantly modify the trapping potentials for multiple rotational states without sacrificing coherences among these states. We demonstrate that magic trapping conditions for multiple rotational states in ultracold 23Na87Rb polar molecule can be created. In addition, we show that spin-decoupled magic trapping can be achieved with an applied static electric field oriented along the magnetic field direction.
An efficient approach for preparing ground states in the context of strongly interacting local quantum field theories on quantum computers is presented. The algorithm belongs to the same class as traditional adiabatic state preparation techniques and methods based on quantum Zeno effect in that it starts with a ground state of an analytically calculable system and evolves the parameters of the Hamiltonian to the one of interest while maintaining the ground state along the path in parameter space. The approach produces the vacuum state in a time proportional to the square-root of the volume, which is a square-root improvement in speed compared to traditional approaches. The approach exploits a novel method for traversing the path in parameter space in which the resources scale linearly with a path length suitably defined in parameter space. Errors due to practical limitations are controlled and do not exhibit secular growth along the path. The final accuracy can be arbitrarily improved with an additive cost, which is independent of the volume and grows slower than logarithmically with the overlap between the state produced and the exact ground state.
In this paper, we explore topological quantum computation augmented by subphases and phase transitions. We commence by investigating the anyon tunneling map, denoted as $\varphi$, between subphases of the quantum double model $\mathcal{D}(G)$ for any arbitrary finite group $G$. Subsequently, we delve into the relationship between $\varphi$ and the Floquet code, and extend the Abelian Floquet code to encompass non-abelian cases. We conclude by demonstrating how phase transitions in both the temporal and spatial directions can enhance the diversity of topological gates for general topological orders described by modular tensor categories.
In this work we present a simulation of the semiconductor electrodes of photoelectrochemical (PEC) water splitting cells based on the nonequilibrium Green's function (NEGF) formalism. While the performance of simple PEC cells can be adequately explained with semi-classical drift-diffusion theory, the increasing interest towards thin film cells and nanostructures in general requires theoretical treatment that can capture the quantum phenomena influencing the charge carrier dynamics in these devices. Specifically, we study a p-type Cu2O electrode and examine the influence of the bias voltage, reaction kinetics and the thickness of the Cu2O layer on the generated photocurrent. The NEGF equations are solved in a self-consistent manner with the electrostatic potential from Poisson's equation, sunlight induced photon scattering and the chemical overpotential required to drive the water splitting reaction. We show that the NEGF simulation accurately reproduces experimental results from both voltammetry and impedance spectroscopy measurements, while providing an energy resolved solution of the charge carrier densities and corresponding currents inside the semiconductor electrode at nanoscale.
The nuclear time-dependent density functional theory (TDDFT) is a tool of choice for describing various dynamical phenomena in atomic nuclei. In a recent study, we reported an extension of the framework - the multiconfigurational TDDFT (MC-TDDFT) model - that takes into account quantum fluctuations in the collective space by mixing several TDDFT trajectories. In this article, we focus on technical and numerical aspects of the model. We outline the properties of the time-dependent variational principle that is employed to obtain the equation of motion for the mixing function. Furthermore, we discuss evaluation of various ingredients of the equation of motion, including the Hamiltonian kernel, norm kernel, and kernels with explicit time derivatives. We detail the numerical methods for resolving the equation of motion and outline the major assumptions underpinning the model. A technical discussion is supplemented with numerical examples that consider collective quadrupole vibrations in $^{40}$Ca, particularly focusing on the issues of convergence, treatment of linearly dependent bases, energy conservation, and prescriptions for the density-dependent part of an interaction.