On the feasibility of truncated Israel-Stewart model in the context of late acceleration

TL;DR

This paper investigates a simplified causal viscous cosmological model based on the truncated Israel-Stewart theory, demonstrating its consistency with observational data and its advantages over other viscous models in explaining late-time cosmic acceleration.

Contribution

It introduces a truncated Israel-Stewart viscous model with analytical solutions and compares its observational viability to other viscous theories, highlighting its feasibility for late Universe acceleration.

Findings

The model predicts a decelerated early universe and a stable de Sitter future.

Estimated universe age is approximately 13.66 Gyr, aligning with observations.

The truncated model is more compatible with astronomical data than other viscous models.

Abstract

A dissipative model of the Universe based on the causal relativistic truncated Israel-Stewart theory is analysed in the context of recent accelerated expansion of the Universe. The bulk viscosity and relaxation time are taken as $\xi=\alpha\rho^s$ and $\tau=\frac{\alpha}{\epsilon\gamma(2-\gamma)}\rho^{s-1}$ respectively. For $s=1/2,$ we found an analytical solution for the Hubble parameter of the model. We have estimated the model parameters by treating $\gamma=1$ and $\gamma$ as a free parameter using the latest cosmological data. The model predicts a prior decelerated phase and an end de Sitter phase as in the standard $\Lambda$CDM model. The dynamical system analysis shows that the prior decelerated epoch is an unstable equilibrium, while the far future de Sitter epoch is stable. The age of the Universe obtained around $13.66$ Gyr, which is close to the recent observations. The second law of thermodynamics is found to be satisfied throughout the evolution in this model. The feasibility of the model has been checked by contrasting with models based on the full Israel-Stewart and the Eckart viscous theories. The truncated viscous model appears more compatible with astronomical observations than the Eckart and full causal viscous models.