Singularity and exit problems in two-dimensional string cosmology

TL;DR

This paper investigates two-dimensional string cosmology models with loop corrections, showing that curvature singularities are smoothed but the models do not naturally evolve towards fixed points with constant dilaton, leaving the exit problem unresolved.

Contribution

It demonstrates that loop-corrected two-dimensional string cosmology models do not resolve the exit problem by failing to reach fixed points with constant dilaton.

Findings

Curvature singularities are smoothed by loop corrections.

Models do not exhibit branch changes despite smoothing.

Exit problem remains unresolved in these models.

Abstract

A broad class of two-dimensional loop-corrected dilaton gravity models exhibit cosmological solutions that interpolate between the string perturbative vacuum and a background with asymptotically flat metric and linearly growing dilaton. The curvature singularities of the corresponding tree-level solutions are smoothed out, but no branch-change occurs. Thus, even in the presence of a non-perturbative potential, the system is not attracted by physically interesting fixed points with constant dilaton, and the exit problem of string cosmology persists.