Mirror Images of String Cosmologies

TL;DR

This paper uses a discrete symmetry of string effective action to generate new string cosmology solutions from known general relativity vacuum solutions, including tilted Bianchi models and oscillating dilaton plane waves.

Contribution

It introduces a method to derive novel string cosmologies from classical vacuum solutions using symmetry transformations, expanding the set of known models.

Findings

Generated a tilted Bianchi type V cosmology from vacuum type VI_h solutions.

Found a plane wave solution with a bounded, oscillating dilaton field from type VII_h models.

Demonstrated the application of discrete symmetries to produce diverse string cosmologies.

Abstract

A discrete symmetry of the four-dimensional string effective action is employed to derive spatially homogeneous and inhomogeneous string cosmologies from vacuum solutions of general relativity that admit two commuting spacelike Killing vectors. In particular, a tilted Bianchi type V cosmology is generated from a vacuum type VI_h solution and a plane wave solution with a bounded and oscillating dilaton field is found from a type ${\rm VII}_h$ model. Further applications are briefly discussed.