Remarks on Tachyon Driven Cosmology

TL;DR

This paper reviews unstable D-brane decay in string theory and explores tachyon-driven cosmological models, revealing bounce solutions and conditions for non-singular universes influenced by a cosmological constant.

Contribution

It applies open-closed string duality to tachyon cosmology, introducing new bounce solutions and analyzing conditions for non-singular evolution.

Findings

Bounce solutions with time reversal symmetry

Universe begins with big bang and ends in big crunch without cosmological constant

Non-singular solutions possible with specific initial conditions and cosmological constant

Abstract

We begin by reviewing the results on the decay of unstable D-branes in type II string theory, and the open-closed string duality proposal that arises from these studies. We then apply this proposal to the study of tachyon driven cosmology, namely cosmological solutions describing the decay of unstable space filling D-branes. This naturally gives rise to a time reversal invariant bounce solution with positive spatial curvature. In the absence of a bulk cosmological constant the universe always begins with a big bang and ends in a big crunch. In the presence of a bulk cosmological constant one may get non-singular cosmological solutions for some special range of initial conditions on the tachyon.