Anisotropic space-times in homogeneous string cosmology

TL;DR

This paper explores a new class of anisotropic, homogeneous solutions in string cosmology, revealing their properties, singularities, and duality behaviors, extending the understanding of early universe models beyond isotropic assumptions.

Contribution

It introduces a novel class of anisotropic, homogeneous string cosmology solutions that generalize known isotropic models and analyzes their properties and symmetries.

Findings

Existence of anisotropic homogeneous solutions in string cosmology.

All solutions have initial singularities and no inflation.

Solutions include behavior under abelian duality.

Abstract

The dynamics of the early universe may have been profoundly influenced by spatial anisotropies. A search for such backgrounds in the context of string cosmology has uncovered the existence of an entire class of (spatatially) homogeneous but not necessarily isotropic space-times, analogous to the class of Bianchi-types in general relativity. Configurations with vanishing cosmological constant but non-vanishing dilaton and antisymmetric field are explicitly found for all types. This is a new class of solutions, whose isotropy limits reproduce all known and, further, all possible FRW-type of models in the string-cosmology context considered. There is always an initial singularity and no inflation. Other features of the general solutions, including their behaviour under abelian duality are are also discussed.