Statistical approaches on the apparent horizon entropy and the generalized second law of thermodynamics

TL;DR

This paper examines how three non-Gaussian entropy measures affect the validity of the generalized second law of thermodynamics in cosmology, finding that the law can be violated depending on entropy parameters.

Contribution

It introduces the analysis of modified Rènyi, Sharma-Mittal, and dual Kaniadakis entropies in the context of the GSL within $\\Lambda CDM$ cosmology, extending previous work on Barrow entropy.

Findings

GSL is conditionally violated for small entropy parameters.

The entropy parameters must be constrained to satisfy GSL.

GSL violation occurs at small redshift values.

Abstract

In this work we have investigated the effects of three nongaussian entropies, namely, the modified R\'enyi entropy (MRE), the Sharma-Mittal entropy (SME) and the dual Kaniadakis entropy (DKE) in the investigation of the generalized second law (GSL) of thermodynamics violation. The GSL is an extension of the second law for black holes. Recently, it was concluded that a total entropy is the sum of the entropy enclosed by the apparent horizon plus the entropy of the horizon itself when the apparent horizon is described by the Barrow entropy. It was assumed that the universe is filled with matter and dark energy fluids. Here, the apparent horizon will be described by MRE, SME, and then by DKE proposals. Since GSL holds for usual entropy, but it is conditionally violated in the extended entropies, this implies that the parameter of these entropies should be constrained in small values in order for the GSL to be satisfied. Hence, we have established conditions where the second law of thermodynamics can or cannot be obeyed considering these three statistical concepts just as it was made in Barrow's entropy. Considering the $\Lambda CDM$ cosmology we can observe that for MRE, SME and DKE, the GSL of thermodynamics is not obeyed for small redshift values.