Anisotropic String Cosmology at Large Curvatures

TL;DR

This paper investigates how the antisymmetric tensor field influences anisotropic expansion in string cosmology at high curvatures, revealing fixed points that regularize solutions and include isotropic initial conditions.

Contribution

It identifies anisotropic fixed points in string cosmology with $\alpha'$ corrections, showing they act as attractors and can encompass isotropic initial states.

Findings

Anisotropic fixed points serve as regularizing attractors.

Attraction basin includes isotropic initial conditions.

Explicit examples provided for different dimensions and ansätze.

Abstract

We study the effect of the antisymmetric tensor field $B_{\mu\nu}$ on the large curvature phase of string cosmology. It is well-known that a non-vanishing value of $H=dB$ leads to an anisotropic expansion of the spatial dimensions. Correspondingly, in the string phase of the model, including $\alpha '$ corrections, we find anisotropic fixed points of the evolution, which act as regularizing attractors of the lowest order solutions. The attraction basin can also include isotropic initial conditions for the scale factors. We present explicit examples at order $\alpha '$ for different values of the number of spatial dimensions and for different ans\"{a}tze for $H$.