Thermodynamics of dark energy interacting with dark matter and radiation

TL;DR

This paper examines the generalized second law of thermodynamics in a cosmological model where dark energy interacts with dark matter and radiation, demonstrating its universal validity regardless of interaction specifics.

Contribution

It provides a general proof that the generalized second law holds in such interacting dark sector models, independent of interaction form or background geometry.

Findings

The generalized second law is always valid in the considered cosmological scenario.

Entropy variation calculations show no violation of thermodynamic laws.

The law's validity is independent of specific interaction details or fluid equations-of-state.

Abstract

We investigate the validity of the generalized second law of thermodynamics, in the cosmological scenario where dark energy interacts with both dark matter and radiation. Calculating separately the entropy variation for each fluid component and for the apparent horizon itself, we show that the generalized second law is always and generally valid, independently of the specific interaction form, of the fluids equation-of-state parameters and of the background geometry.