# Exact analytical solution for an Israel-Stewart Cosmology

## TL;DR

This paper presents an exact analytical solution for a cosmological model with dissipative matter in the Israel-Stewart framework, exploring conditions for accelerated expansion and stability, with implications for entropy production and sound speed.

## Contribution

It provides a novel exact solution in Israel-Stewart cosmology with specific relations for viscous parameters, analyzing stability and late-time acceleration.

## Key findings

- Accelerated expansion occurs for  er 1/18.
- Stable solutions are identified at critical parameter values.
- Positive entropy production constrains model parameters.

## Abstract

In this article we report a novel analytic solution for a cosmological model with a matter content described by a one component dissipative fluid, in the framework of the causal Israel-Stewart theory. Some physically well motivated analytical relations for the bulk viscous coefficient, the relaxation time and a bariotropic equation of state are postulated. We study within the parameter space, which label the solution, a suited region compatible with an accelerated expansion of the universe for late times, as well as stability properties of the solution at the critical parameter values $ \gamma = 1$ and for $ s = 1/2 $. We study as well the consequences that arise from the positiveness of the entropy production along the time evolution. In general, the accelerated expansion at late times is only possible when $\epsilon\geq 1/18$, which implies a very large non-adiabatic contribution the speed of sound.