Axions and the Graceful Exit Problem in String Cosmology

TL;DR

This paper investigates the challenges of transitioning smoothly from pre-big-bang inflation in string cosmology, demonstrating that adding axions and potentials does not resolve the fundamental no-go theorem preventing a graceful exit.

Contribution

It extends the no-go theorem in string cosmology by including axions and potentials, showing the branch change remains impossible for graceful exit.

Findings

Adding axions does not enable a graceful exit.

The no-go theorem is extended to more general axion/dilaton potentials.

Branch change remains impossible in the generalized scenario.

Abstract

We reexamine the graceful exit problem in the Pre-Big-Bang inflationary scenario. The dilaton-gravity action is generalized by adding the axion and a general axion/dilaton potential. We provide a phase space analysis of the dynamics which leads us to extend the previous no-go theorem and rule out the branch change necessary for graceful exit in this context.