Dynamical Stability of Bulk Viscous Isotropic and Homogeneous Universe

Qanitah Ama-Tul-Mughani,Muhammad Sharif

doi:10.3390/universe5080185

Abstract

In this paper, we study the phase space portrait of homogeneous and isotropic universe by taking different coupling functions between dark energy models and bulk viscous dark matter. The dimensionless quantities are introduced to establish an autonomous set of equations. To analyze the stability of the cosmos, we evaluate critical points and respective eigenvalues for different dynamical quantities. For bulk viscous matter and radiation in tachyon coupled field, these points show stable evolution when γ ≫ δ but accelerated expansion of the universe for δ > 1 9 . The stability of the universe increases for some stationary points which may correspond to the late-time expansion for the coupled phantom field.

Highlights

Recent astronomical observations such as type Ia supernova and cosmic microwave background radiations appear to be fairly compatible with the current cosmic accelerated expansion.These observational pieces of evidence have categorized the universe into four basic epochs
Sharif and Mumtaz [25] studied the phase space analysis of locally rotationally symmetric (LRS) Bianchi type I universe by taking different coupling functions between DE models and dark matter
The impact of bulk viscosity on the stability of FRW universe has been examined through different coupling functions between dark matter and DE models

Summary

Introduction

Recent astronomical observations such as type Ia supernova and cosmic microwave background radiations appear to be fairly compatible with the current cosmic accelerated expansion. Shahalam et al [23] analyzed the stability as well as accelerated behavior of the universe through the interaction of scalar field models with dark matter in the gravitational background of the FRW universe. Sharif and Mumtaz [25] studied the phase space analysis of locally rotationally symmetric (LRS) Bianchi type I universe by taking different coupling functions between DE models and dark matter. We explore stability as well as expanding behavior of FRW universe, by considering the interaction of DE models with bulk viscous dark matter, through phase space analysis.

Dynamical Equations

Coupled Phantom Field

Coupled Tachyon Dynamics

Conclusions