Classical Inhomogeneities in String Cosmology

TL;DR

This paper extends inhomogeneous pre-big bang cosmology models by incorporating moduli and antisymmetric tensor fields, analyzing their effects on early universe dynamics, inflation, and duality symmetries near the big bang singularity.

Contribution

It provides a generalized quasi-homogeneous solution including moduli and axion fields, estimates inflation during the pre-big bang era, and explores duality symmetries in this context.

Findings

Quantitative estimate of inflation during pre-big bang era

Generalized solutions with moduli and axion fields

Discussion of duality symmetries near singularity

Abstract

We generalize previous work on inhomogeneous pre-big bang cosmology by including the effect of non-trivial moduli and antisymmetric-tensor/axion fields. The general quasi-homogeneous asymptotic solution---as one approaches the big bang singularity from perturbative initial data---is given and its range of validity is discussed, allowing us to give a general quantitative estimate of the amount of inflation obtained during the perturbative pre-big bang era. The question of determining early-time ``attractors'' for generic pre-big bang cosmologies is also addressed, and a motivated conjecture is advanced. We also discuss S-duality-related features of the solutions, and speculate on the way an asymptotic T-duality symmetry may act on moduli space as one approaches the big bang.