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

In this work we have investigated the effects of three nongaussian entropies, namely, the modified Renyi 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 to obey the GSL of thermodynamics. 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 will notice that for MRE, SME and DKE, the GSL of thermodynamics is not obeyed for small redshift values. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

This work investigates the effects of three nongaussian entropies, namely, the modified Renyi entropy (MRE), the Sharma-Mittal entropy (SME), and the dual Kaniadakis entropy (DKE), on the violation of the generalized second law (GSL) of thermodynamics. It is found that the GSL may be violated when considering these extended entropies, and the parameters of these entropies need to be constrained to small values to obey the GSL. The study also reveals that for MRE, SME, and DKE, the GSL is not obeyed for small redshift values in the Lambda CDM cosmology.