The graceful exit in pre-big bang string cosmology

TL;DR

This paper investigates the conditions under which the pre-big bang string cosmology scenario can smoothly transition between phases, considering general classical and quantum corrections, and ensuring compatibility with entropic bounds.

Contribution

It introduces a comprehensive analysis of classical and quantum corrections to achieve a smooth graceful exit in pre-big bang cosmology, expanding the understanding of viable transition mechanisms.

Findings

Identifies parameter regions allowing smooth transition between cosmological branches.

Demonstrates solutions can satisfy entropic bounds on singularity-free cosmologies.

Shows quantum loop corrections influence the graceful exit conditions.

Abstract

We re-examine the graceful exit problem in the pre-big bang scenario of string cosmology, by considering the most general time-dependent classical correction to the Lagrangian with up to four derivatives. By including possible forms for quantum loop corrections we examine the allowed region of parameter space for the coupling constants which enable our solutions to link smoothly the two asymptotic low-energy branches of the pre-big bang scenario, and observe that these solutions can satisfy recently proposed entropic bounds on viable singularity free cosmologies.