Cosmological Bounce Scenario with a Novel Parametrization of Bulk Viscosity

TL;DR

This paper introduces a new parametrization of bulk viscosity in cosmology, leading to exact non-singular bounce solutions within general relativity, and demonstrates their stability and compliance with energy conditions.

Contribution

It proposes a novel bulk viscosity form that enables exact bounce solutions and analyzes their stability and energy condition violations in early universe cosmology.

Findings

NEC and SEC are violated at the bounce point

DEC is satisfied throughout the evolution

Bounce solutions are stable under linear perturbations

Abstract

In this work, we have studied how incorporating viscous fluids leads to exact bounce cosmological solutions in general relativity (GR) framework. Specifically, we propose a novel parameterization of bulk viscosity coefficient of the form $\zeta = \zeta_0 (t-t_0)^{-2n} H$, where $\zeta_0$, $n$ being some positive constants and $t_0$ is the bounce epoch. We investigate how this form of bulk viscosity may assist in explaining the early universe's behaviour, with a particular focus on non-singular bounce scenario by studying the various energy conditions and other related cosmological observables and how the model parameters affect the evolution of the Universe. We demonstrate that the NEC and SEC violation occurs at the bounce point while DEC is satisfied. Finally, we carried out a stability check based on linear order perturbation to the Hubble parameter. We found that the perturbation vanishes asymptotically at later times, which indicates a stable behaviour of the bounce scenario