Exact solutions in two-dimensional string cosmology with back reaction

TL;DR

This paper derives exact two-dimensional string cosmology solutions with back reaction, including a nonsingular inflationary exit and a duality-related singular solution, highlighting back reaction's crucial role.

Contribution

It provides explicit analytic solutions in 2D dilaton gravity with back reaction, revealing their impact on cosmological evolution and singularity structure.

Findings

One solution shows a nonsingular graceful exit from inflation.

A duality-related solution exists only in the pre-big-bang epoch.

Back reaction significantly influences the geometry and singularity properties.

Abstract

We present analytic cosmological solutions in a model of two-dimensional dilaton gravity with back reaction. One of these solutions exhibits a graceful exit from the inflationary to the FRW phase and is nonsingular everywhere. A duality related second solution is found to exist only in the ``pre-big-bang'' epoch and is singular at $\tau = 0$. In either case back reaction is shown to play a crucial role in determining the specific nature of these geometries.