Towards A Nonsingular Tachyonic Big Crunch

TL;DR

This paper explores a string theory-based cosmological model featuring a nonsingular, static tachyon condensate phase with fixed dilaton, potentially describing a Hagedorn phase in string gas cosmology.

Contribution

It introduces a novel effective field theory framework coupling gravity, dilaton, and tachyon fields with string gases, demonstrating a nonsingular phase with fixed dilaton.

Findings

Existence of a nonsingular, static tachyon condensate phase

Demonstration of a fixed dilaton in a stable phase

Time-reversal symmetry leading to a Hagedorn phase description

Abstract

We discuss an effective field theory background containing the gravitational field, the dilaton and a closed string tachyon, and couple this background to a gas of fundamental strings and D strings. Allowing for the possibility of a non-vanishing dilaton potential of Casimir type, we demonstrate the possibility of obtaining a nonsingular, static tachyon condensate phase with fixed dilaton. The time reversal of our solution provides a candidate effective field theory description of a Hagedorn phase of string gas cosmology with fixed dilaton.