String Cosmology of the D-brane Universe

TL;DR

This paper investigates how string theory D-branes influence early universe cosmology, showing that anisotropic expansion can become isotropic over time due to dilaton dynamics and curvature effects.

Contribution

It introduces attractor solutions in string-inspired anisotropic cosmology with D-branes, demonstrating conditions for isotropy recovery through dilaton stabilization and curvature effects.

Findings

Anisotropic universe expands while D-brane terms dominate.

Isotropy is restored as the dilaton rolls down.

Dilaton stabilization leads to isotropic cosmological solutions.

Abstract

We analyze homogeneous anisotropic cosmology driven by the dilaton and the self-interacting ``massive'' antisymmetric tensor field which are indispensable bosonic degrees with the graviton in the NS-NS sector of string theories with D-branes. We found the attractor solutions for this system, which show the overall features of general solutions, and confirmed it through numerical analysis. The dilaton possesses the potential due to the presence of the D-brane and the curvature of extra dimensions. In the presence of the non-vanishing antisymmetric tensor field, the homogeneous universe expands anisotropically while the D-brane term dominates. The isotropy is recovered as the dilaton rolls down and the curvature term dominates. With the stabilizing potential for the dilaton, the isotropy can also be recovered.