Constraining the bulk viscous coefficients in a viscous universe with cosmological constant

TL;DR

This paper investigates the effects of bulk viscosity in a universe with a cosmological constant, constraining viscous coefficients using observational data and analyzing their impact on cosmic evolution.

Contribution

It introduces a general form for bulk viscous coefficients in a $ ext{Lambda}$CDM universe and derives observational constraints on these coefficients.

Findings

Constrained bulk viscous coefficients using Pantheon supernova data.

Analyzed thermodynamic evolution and estimated the universe's age with viscous effects.

Provided bounds on viscosity parameters consistent with observational data.

Abstract

In this paper we consider dissipative effects in $\Lambda$CDM model, i.e., we consider a universe with cosmological constant having viscous matter. We assume the most general form for bulk viscous coefficient, $\zeta=\zeta_{0}+\zeta_{1}\frac{\dot{a}}{a}+\zeta_{2}\frac{\ddot{a}}{\dot{a}}$ and obtained various constrains for $\zeta$'s . We also studied the background study of the model with $\zeta=\zeta_{0}$ and $\zeta=\zeta_{1}\frac{\dot{a}}{a}$. Extracted the value of $\zeta_1$ using the Pantheon data and also obtained its thermodynamic evolution and the age.