Generalized holographic Ricci dark energy and generalized second law of thermodynamics in Bianchi Type I universe

TL;DR

This paper investigates the generalized second law of thermodynamics in an anisotropic Bianchi type I universe with holographic Ricci dark energy, revealing its partial validity and connection to galaxy formation processes.

Contribution

It introduces a study of thermodynamics and dark energy in an anisotropic universe, highlighting the law's partial violation and the role of galaxy formation in entropy changes.

Findings

The dark energy behaves matter-like early and phantom-like later.

The universe transitions from high anisotropy to homogeneity.

The generalized second law is not always valid, especially near the past and future.

Abstract

Generalized second law of thermodynamics in the Bianchi type I universe with the generalized holographic Ricci dark energy model is studied in this paper. The behavior of dark energy's equation of state parameter indicates that it is matter-like in the early time of the universe but phantom-like in the future. By analysing the evolution of the deviations of state parameter and the total pressure of the universe, we find that for an anisotropic Bianchi type I universe, it transits from a high anisotropy stage to a more homogeneous stage in the near past. Using the normal entropy given by Gibbs' law of thermodynamics, it is proved that the generalized second law of thermodynamics does not always satisfied throughout the history of the universe when we assume the universe is enclosed by the generalized Ricci scalar radius $R_{gr}$. It becomes invalid in the near past to the future, and the formation of the galaxies will be helpful in explaining such phenomenon, for that the galaxies's formation is an entropy increase process. The negative change rates of the horizon entropy and internal entropy occur in different period indicates that the influences of galaxies formation is wiped from internal to the universe's horizon.