Obinna Umeh

How do we appropriately fit a model based on an idealised Friedmann-Lema{\i}tre Robertson-Walker (FLRW) spacetime to observations made from a single location in a lumpy Universe? We address this question for surveys that measure the imprints of the Baryon Acoustic Oscillation (BAO) in galaxy distribution and the peak apparent magnitude of the type 1A supernova (SN1A). These observables are related to the cosmological model through the Alcock-Paczynski parameters and the distance-redshift relation. Using the corresponding inhomogeneous spacetime expressions of these as observed data, we perform a parameter inference assuming that the background FLRW model is the correct model of the universe. This process allows us to estimate the best fit Hubble rate and the deceleration parameter. We find that the inferred Hubble rate from the monopole of the Alcock-Paczynski parameters is in tension with the Hubble rate determined using the distance-redshift relation. The latter gives the best fit Hubble rate for the cosmological expansion. The constraint on the Hubble rate from the Alcock-Paczynski parameters is contaminated by the environment. When the environmental contribution is restricted to modes in the Hubble flow, we find about (9-12)\% discrepancy in the Hubble rate. Finally, we comment on the insufficiency of the method of cosmography in constraining the deceleration parameter.

Nathaniel Starkman, Glenn D. Starkman, Harrison Winch, Jagjit Singh Sidhu

Recently, four remarkably straight very brief flashes of light were captured on video in Perth, Australia within 0.5s of one another. Straight lightning was recently identified as a prediction of macroscopic dark matter (macros) -- a broad class of alternative candidates to particle dark matter. A sufficiently large macro passing through the atmosphere producing a straight column ofplasma would produce fluorescence, or, under atmospheric conditions conducive to lightning, seeda very straight lightning strike visible to the naked eye. Other explanations are considered, but areproblematic.

M.-A. Sanchis-Lozano, F. Melia, M. López-Corredoira, N. Sanchis-Gual

Context. The existence of a maximum correlation angle ($\theta_{max} \gtrsim 60^{\circ}$) in the two-point angular temperature correlations of cosmic microwave background (CMB) radiation, measured by WMAP and Planck, stands in sharp contrast to the prediction of standard inflationary cosmology, in which the correlations should extend across the full sky (i.e., $180^{\circ}$). The introduction of a hard lower cutoff ($k_{min}$) in the primordial power spectrum, however, leads naturally to the existence of $\theta_{max}$. Among other cosmological anomalies detected in these data, an apparent dominance of odd-over-even parity multipoles has been seen in the angular power spectrum of the CMB. This feature, however, may simply be due to observational contamination in certain regions of the sky. Aims. In attempting to provide a more detailed assessment of whether this odd-over-even asymmetry is intrinsic to the CMB, we therefore proceed in this paper, first, to examine whether this odd-even parity imbalance also manifests itself in the angular correlation function and, second, to examine in detail the interplay between the presence of $\theta_{max}$ and this observed anomaly. Methods. We employed several parity statistics and recalculated the angular correlation function for different values of the cutoff $k_{min}$ in order to optimize the fit to the different Planck 2018 data. Results. We find a phenomenological connection between these features in the data, concluding that both must be considered together in order to optimize the theoretical fit to the Planck 2018 data. Conclusions. This outcome is independent of whether the parity imbalance is intrinsic to the CMB, but if it is, the odd-over-even asymmetry would clearly point to the emergence of new physics.