The fate of classical tensor inhomogeneities in pre-big-bang string cosmology

TL;DR

This paper investigates whether dilaton-driven inflation in pre-big-bang string cosmology can smooth out initial classical tensor inhomogeneities, finding it requires an extremely small initial string coupling to do so.

Contribution

It demonstrates that dilaton-driven inflation does not naturally eliminate classical tensor inhomogeneities unless the initial string coupling is extraordinarily small.

Findings

Dilaton-driven inflation fails to smooth out tensor inhomogeneities without very small initial coupling

Initial string coupling must be less than 10^(-35) for inhomogeneities to be ironed out

Classical tensor inhomogeneities are resilient in pre-big-bang string cosmology

Abstract

In pre-big-bang string cosmology one uses a phase of dilaton-driven inflation to stretch an initial (microscopic) spatial patch to the (much larger) size of the big-bang fireball. We show that the dilaton-driven inflationary phase does not naturally iron out the initial classical tensor inhomogeneities unless the initial value of the string coupling is smaller than 10^(-35).