Bouncing Anisotropic Universes with Varying Constants

TL;DR

This paper explores how varying the fine structure constant in a modified cosmological theory can lead to bouncing, isotropizing, or oscillating universe models, providing new insights into early universe dynamics.

Contribution

It introduces a model where a varying fine structure constant causes a ghost scalar field, resulting in bouncing and oscillating anisotropic universe solutions.

Findings

Bouncing cosmologies due to ghost scalar field dominance

Isotropization through energy exchange mechanisms

Existence of stable anisotropic oscillations around static universe

Abstract

We examine the evolution of a closed, homogeneous and anisotropic cosmology subject to a variation of the fine structure 'constant', \alpha, within the context of the theory introduced by Bekenstein, Sandvik, Barrow and Magueijo, which generalises Maxwell's equations and general relativity. The variation of \alpha permits an effective ghost scalar field, whose negative energy density becomes dominant at small length scales, leading to a bouncing cosmology. A thermodynamically motivated coupling which describes energy exchange between the effective ghost field and the radiation field leads to an expanding, isotropizing sequence of bounces. In the absence of entropy production we also find solutions with stable anisotropic oscillations around a static universe.