Dark energy with an Anisotropic Equation of State

Abstract

We investigate cosmologies where the accelerated expansion of the universe is driven by a fluid with an anisotropic equation of state. If dark energy equation of state is anisotropic, the expansion rate of the universe becomes direction dependent at late times. We show that such models are cosmologically viable. We model such scenarios within axisymmetric limit, described by the Bianchi I, Bianchi III and Kantowsk-Sachs geometries. A skewness parameter is introduced to quantify the deviation of pressure from isotropy. We study the dynamics of the background expansion in these models. The fixed points are found with the aim of uncovering their stability and employing them to device possibly realistic cosmological models.