Irreversible Processes in a Universe modelled as a mixture of a Chaplygin gas and radiation

TL;DR

This paper investigates the evolution of a universe modeled as a mixture of Chaplygin gas and radiation, incorporating irreversible processes, and compares it with a radiation-quintessence mixture, revealing differences in acceleration and energy density behaviors.

Contribution

It introduces a novel analysis of irreversible processes in a Chaplygin gas and radiation universe model, comparing its dynamics with a radiation-quintessence mixture.

Findings

Both models show a transition from deceleration to acceleration.

The Chaplygin gas model exhibits a more pronounced acceleration slope.

Chaplygin gas energy density stabilizes earlier than quintessence.

Abstract

The evolution of a Universe modelled as a mixture of a Chaplygin gas and radiation is determined by taking into account irreversible processes. This mixture could interpolate periods of a radiation dominated, a matter dominated and a cosmological constant dominated Universe. The results of a Universe modelled by this mixture are compared with the results of a mixture whose constituents are radiation and quintessence. Among other results it is shown that: (a) for both models there exists a period of a past deceleration with a present acceleration; (b) the slope of the acceleration of the Universe modelled as a mixture of a Chaplygin gas with radiation is more pronounced than that modelled as a mixture of quintessence and radiation; (c) the energy density of the Chaplygin gas tends to a constant value at earlier times than the energy density of quintessence does; (d) the energy density of radiation for both mixtures coincide and decay more rapidly than the energy densities of the Chaplygin gas and of quintessence.