Rotation in string cosmology

TL;DR

This paper presents exact rotating and expanding cosmological solutions within string theory, featuring shear-free, causal models that preserve isotropy and include nontrivial dilaton and axion fields.

Contribution

It introduces new exact solutions in string cosmology with rotation, expanding previous models to include shear-free, causal, and isotropic properties with nontrivial scalar fields.

Findings

Models are spatially homogeneous Bianchi type IX

Solutions are shear-free and causal, with no closed timelike curves

Dilaton and axion fields are nontrivial in these solutions

Abstract

We describe exact cosmological solutions with rotation and expansion in the low-energy effective string theory. These models are spatially homogeneous (closed Bianchi type IX) and they belong to the family of shear-free metrics which are causal (no closed timelike curves are allowed), admit no parallax effects and do not disturb the isotropy of the background radiation. The dilaton and the axion fields are nontrivial, in general, and we consider both cases with and without the central charge (effective cosmological constant).