Dynamics of locally rotationally symmetric Bianchi type VIII cosmologies with anisotropic matter

TL;DR

This paper investigates how anisotropic matter influences the evolution of Bianchi type VIII cosmologies, revealing that near-isotropic matter behaves like perfect fluids, while high anisotropy leads to distinct dynamics.

Contribution

It introduces a dynamical system analysis of Bianchi type VIII models with a generalized anisotropic matter family, extending understanding beyond perfect fluids.

Findings

Near-isotropic matter yields dynamics similar to perfect fluids.

High anisotropy causes significant deviations from vacuum and perfect fluid behavior.

The study characterizes asymptotic behaviors of these cosmologies.

Abstract

This paper is a study of the effects of anisotropic matter sources on the qualitative evolution of spatially homogenous cosmologies of Bianchi type VIII. The analysis is based on a dynamical system approach and makes use of an anisotropic matter family developed by Calogero and Heinzle which generalises perfect fluids and provides a measure of deviation from isotropy. Thereby the role of perfect fluid solutions is put into a broader context. The results of this paper concern the past and future asymptotic dynamics of locally rotationally symmetric solutions of type VIII with anisotropic matter. It is shown that solutions whose matter source is sufficiently close to being isotropic exhibit the same qualitative dynamics as perfect fluid solutions. However a high degree of anisotropy of the matter model can cause dynamics to differ significantly from the vacuum and perfect fluid case.