Bianchi type III models with anisotropic dark energy

TL;DR

This paper derives exact solutions for Bianchi type-III cosmological models with anisotropic dark energy, showing that the universe can become isotropic over time even with anisotropic fluids, and explores different expansion scenarios.

Contribution

It provides new exact solutions for anisotropic Bianchi type-III models with anisotropic dark energy and analyzes their isotropization behavior over cosmic time.

Findings

Universe approaches isotropy monotonically.

Anisotropic fluid evolves into cosmological constant.

Accelerating models isotropize at late times.

Abstract

The general form of the anisotropy parameter of the expansion for Bianchi type-III metric is obtained in the presence of a single diagonal imperfect fluid with a dynamically anisotropic equation of state parameter and a dynamical energy density in general relativity. A special law is assumed for the anisotropy of the fluid which reduces the anisotropy parameter of the expansion to a simple form. The exact solutions of the Einstein field equations, under the assumption on the anisotropy of the fluid, are obtained for exponential and power-law volumetric expansions. The isotropy of the fluid, space and expansion are examined. It is observed that the universe can approach to isotropy monotonically even in the presence of an anisotropic fluid. The anisotropy of the fluid also isotropizes at later times for accelerating models and evolves into the well-known cosmological constant in the model for exponential volumetric expansion.