Qualitative Analysis of Viscous Fluid Cosmological Models satisfying the Israel-Stewart theory of Irreversible Thermodynamics

TL;DR

This paper explores the qualitative behavior of isotropic, homogeneous viscous fluid cosmological models using the Israel-Stewart theory, revealing how a free parameter influences model dynamics and inflation conditions.

Contribution

It introduces a dynamical systems approach to viscous cosmological models based on the Israel-Stewart theory, highlighting differences from Eckart theory and analyzing inflation conditions.

Findings

Model behavior varies significantly with the free parameter.

The models can exhibit inflation under certain conditions.

Differences from Eckart theory models are identified.

Abstract

Isotropic and spatially homogeneous viscous fluid cosmological models are investigated using the truncated Israel-Stewart theory of irreversible thermodynamics to model the bulk viscous pressure. The governing system of differential equations is written in terms of dimensionless variables and a set of dimensionless equations of state is then utilized to complete the system. The resulting dynamical system is analyzed using geometric techniques from dynamical systems theory to find the qualitative behaviour of the Friedmann-Robertson-Walker models with bulk viscosity. In these models there exists a free parameter such that the qualitative behaviour of the models can be quite different (for certain ranges of values of this parameter) from that found in models satisfying the Eckart theory studied previously. In addition, the conditions under which the models inflate are investigated.