Anisotropic 'hairs' in string cosmology

TL;DR

This paper examines whether pre-big-bang string cosmologies can naturally resolve the isotropy problem, finding that unlike potential inflation models, initial anisotropies persist during pre-big-bang inflation.

Contribution

It demonstrates that initial anisotropies do not decay in pre-big-bang inflation, contrasting with potential inflation models and highlighting a key difference in string-inspired cosmologies.

Findings

Initial anisotropies persist during pre-big-bang inflation.

Contrasts with potential inflation models where anisotropies decay.

Implications for the isotropy problem in string cosmology.

Abstract

In this letter we investigate whether the isotropy problem is naturally solved in inflationary cosmologies inspired by string theory, so called pre-big-bang cosmologies. We find that, in contrast to what happens in the more common 'potential inflation' models, initial anisotropies do not decay during pre-big-bang inflation.