Gravitational entropy of cosmic expansion

TL;DR

This paper investigates the concept of gravitational entropy in cosmic voids, demonstrating its growth over time within non-perturbative General Relativity and analyzing the effects of a cosmological constant on this process.

Contribution

It applies a recent gravitational entropy proposal to cosmic voids using LTB models, showing entropy growth and the impact of a cosmological constant.

Findings

Gravitational entropy increases from post-inflation to late times.

A positive cosmological constant suppresses entropy growth.

Entropy reaches a stable value faster with a cosmological constant.

Abstract

We apply a recent proposal to define "gravitational entropy" to the expansion of cosmic voids within the framework of non-perturbative General Relativity. By considering CDM void configurations compatible with basic observational constraints, we show that this entropy grows from post-inflationary conditions towards a final asymptotic value in a late time fully non-linear regime described by the Lemaitre-Tolman-Bondi (LTB) dust models. A qualitatively analogous behavior occurs if we assume a positive cosmological constant consistent with a $\Lambda$-CDM background model. However, the $\Lambda$ term introduces a significant suppression of entropy growth with the terminal equilibrium value reached at a much faster rate.