A GREAT model comparison against the cosmological constant

Recently, a covariant formulation of non-equilibrium phenomena in the context of General Relativity was proposed in order to explain from first principles the observed accelerated expansion of the Universe, without the need for a cosmological constant, leading to the GREA theory. Here, we confront the GREA theory against the latest cosmological data, including type Ia supernovae, baryon acoustic oscillations, the cosmic microwave background (CMB) radiation, Hubble rate data from the cosmic chronometers and the recent $H_0$ measurements. We perform Markov Chain Monte Carlo analyses and a Bayesian model comparison, by estimating the evidence via thermodynamic integration, and find that when all the aforementioned data are included, but no prior on $H_0$, the difference in the log-evidence is $\\sim -9$ in favor of GREA, thus resulting in overwhelming support for the latter over the cosmological constant and cold dark matter model ($Λ$CDM). When we also include priors on $H_0$, either from Cepheids or the Tip o

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The effect of GREA on the gravitational collapse of neutron stars

General Relativistic Entropic Acceleration (GREA) gives a general framework in which to study multiple out-of-equilibrium phenomena in the context of general relativity, like the late accelerated expansion of the universe or the formation of galaxies and the large scale structure of the universe. Here we analyze the conditions for collapse of a star of degenerate neutrons in the presence of entropy production due to the gravitational collapse itself. We find that the final mass and radius of the neutron star differs from that obtained with the adiabatic Tolman-Oppenheimer-Volkoff equation by a factor of order 15\\%. We also find that the minimum mass of a neutron star is $\\sim 1.1\\,M_\\odot$ and the maximum mass around $2.4\\,M_\\odot$. We discuss the possible implications for the search and interpretation of binary coalescing systems like neutron stars and neutron star-black holes detectable via their multimessenger (gravitational and electromagnetic wave) emission upon merging.

arxiv.org