The Bulk Viscous String Cosmology in An Anisotropic Universe With Late Time Acceleration

TL;DR

This paper presents a cosmological model with bulk viscous strings in an anisotropic universe, showing that viscosity influences the transition from deceleration to acceleration, aligning with late-time cosmic acceleration observations.

Contribution

It introduces a Bianchi type II string cosmology model with bulk viscosity, demonstrating its role in universe acceleration and the dominance shift between particles and strings.

Findings

Bulk viscosity causes universe acceleration.

Particles dominate over strings with viscosity.

Models evolve from deceleration to acceleration.

Abstract

A model of a cloud formed by massive strings is used as a source of Bianchi type II. We assumed that the expansion $(\theta)$ in the model is proportional to the shear $(\sigma)$. To get exact solution, we have considered the equation of state of the fluid to be in the stiff form. It is found that the bulk viscosity plays a very important rule in the history of the universe. In presence of bulk viscosity the particles dominate over strings whereas in absence of it, strings dominate over the particles which is not in consistence with the recent observations. Also we observe that the viscosity caused the expansion of the universe to be accelerating. Our models are evolving from an early decelerating phase to a late time accelerating phase. The physical and geometrical behavior of these models are discussed.