Can the Type-IIB axion prevent Pre-big Bang inflation?

TL;DR

This paper investigates whether a Type-IIB axion can prevent or enable superinflation in Pre-big Bang cosmological models, revealing specific conditions under which inflation occurs or is suppressed.

Contribution

It demonstrates that while most axions do not affect inflation, certain classes can entirely prevent superinflation in these models.

Findings

A narrow parameter range allows superinflation.

Some axions can completely inhibit inflation.

Initial conditions and collapse extensions are briefly discussed.

Abstract

We look at the possibility of superinflationary behavior in a class of anisotropic Type-IIB superstring cosmologies in the context of Pre-big Bang scenario and find that there exists a rather narrow range of parameters for which these models inflate. We then show that, although in general this behavior is left untouched by the introduction of a Ramond-Ramond axion field through a SL(2,R) rotation, there exists a particular class of axions for which inflation disappears completely. Asymptotic past initial conditions are briefly discussed, and some speculations on the possible extension of Pre-big Bang ideas to gravitational collapse are presented.