Joaquin Housset | Searcharxiv

arXiv2025

First-order phase transitions and cosmic evolution: thermodynamic approach to generalized holographic dark energy

Focusing on the description of cosmic evolution at late times, this study examines a generalized holographic dark energy (HDE) framework constructed via a polynomial expansion in the Hubble parameter, which includes contributions proportional to $H^{2}$, $H^{4}$, and $H^{6}$, introduced through a variable parameter within the standard holographic formula. The analysis is carried out in the context of a spatially flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) Universe, consisting of non-interacting matter together with the HDE fluid. We obtain the full set of Friedmann equations to investigate cosmic evolution and then analyze the system to determine whether thermodynamic $P - v$ type phase transitions can occur.

gr-qc↗

arXiv2024

Cosmological FLRW phase transitions and micro-structure under Kaniadakis statistics

This article is devoted to the study of the thermodynamics phase transitions and critical phenomena of an FLRW cosmological model under the so-called Kaniadakis's statistics. The equation of state is derived from the corrected Friedmann field equations and the thermodynamics unified first law. This reveals the existence of non-trivial critical points where a first-order phase transition takes place. The system behaves as an "inverted" van der Waals fluid in this concern. Interestingly, the numerical values of the critical exponents are the same as those of the van der Waals system. Besides, to obtain more insights into the thermodynamics description, the so-called Ruppeiner's geometry is studied through the normalized scalar curvature, disclosing this invariant zone where the system undergoes repulsive/attractive interactions. Near the critical point, this curvature provides again the same critical exponent and universal constant value as for van der Waals fluid.

gr-qc↗