Kantowski-Sachs Einstein-Aether Scalar Field Cosmological Models

TL;DR

This paper explores anisotropic, positively curved cosmological models within Einstein-aether theory, revealing conditions for late-time acceleration and how scalar field coupling affects inflationary parameters.

Contribution

It introduces a new class of Einstein-aether scalar field models with a generalized exponential potential and analyzes their stability and late-time behavior.

Findings

Existence of accelerating future attractors in certain parameter ranges.

Coupling allows for larger inflationary parameter values than in general relativity.

Stability analysis of equilibrium points supports potential for late-time acceleration.

Abstract

A class of positive curvature spatially homogeneous but anisotropic cosmological models within an Einstein-aether gravitational framework are investigated. The matter source is assumed to be a scalar field which is coupled to the expansion of the aether field through a generalized exponential potential. The evolution equations are expressed in terms of expansion-normalized variables to produce an autonomous system of ordinary differential equations suitable for a numerical and qualitative analysis. An analysis of the local stability of the equilibrium points indicates that there exists a range of values of the parameters in which there exists an accelerating expansionary future attractor. In general relativity, scalar field models with an exponential potential $V=V_0e^{-2k\phi}$ have a late-time inflationary attractor for $k^2<\frac{1}{2}$; however, it is found that the existence of the coupling between the aether and scalar fields allows for arbitrarily large values of the parameter $k$.