Dark Energy and Search for the Generalized Second Law

TL;DR

This paper investigates the role of modified Chaplygin gas as a dark energy candidate in an accelerated universe, analyzing conditions for the validity of the generalized second law of thermodynamics and the positivity of phantom fluid temperature.

Contribution

It explores the thermodynamic viability of modified Chaplygin gas as dark energy, considering the observer's event horizon and conditions for the generalized second law.

Findings

Conditions for the validity of the generalized second law are derived.

The positivity of the phantom fluid temperature is maintained under certain conditions.

Modified Chaplygin gas can be a consistent dark energy candidate within thermodynamic constraints.

Abstract

The discovery of accelerated Hubble expansion in the SNIa data and the observed power spectrum of the microwave background radiation provide an ample support for Dark energy and Dark matter. Except for the so far well-known facts that cold dark matter (or simply dark matter) is pressureless, and dark energy has a negative pressure, the nature of these two still remains a complete mystery. The mystery facilitates different consideration. In one hand, dark matter and dark energy are assumed as distinct entities, and other interpretation is that both are different manifestation of a common structure, often referred as quartessence. Chaplygin gas, a perfect fluid also favours the second interpretation. Here, we consider modified chaplygin gas as dark energy candidate. Taking into account the existence of the observer's event horizon in accelerated universe, we find the condition where the generalized second law of gravitational thermodynamics is valid and the positivity of the temperature of the phantom fluid remains intact.