Isotropization of two-component fluids

TL;DR

This paper investigates how two non-interacting perfect fluids, one tilted and one non-tilted, influence the late-time isotropization of Bianchi type V cosmological models, with implications for the cosmic no-hair theorem.

Contribution

It provides a global analysis of the gravitational field equations for two-fluid Bianchi models, highlighting conditions for isotropization and extending the cosmic no-hair theorem.

Findings

Conditions under which isotropization occurs in two-fluid models

Impact of tilted fluids on the cosmic no-hair theorem

Global phase space understanding of Bianchi type V models

Abstract

We consider the problem of late-time isotropization in spatially homogeneous but anisotropic cosmological models when the source of the gravitational field consists of two non-interacting perfect fluids -- one tilted and one non-tilted. In particular, we study irrotational Bianchi type V models. By introducing appropriate dimensionless variables, a full global understanding of the state space of the gravitational field equations becomes possible. The issue of isotropization can then be addressed in a simple fashion. We also discuss implications for the cosmic ``no-hair'' theorem for Bianchi models when part of the source is a tilted fluid.