Bouncing universe and non-BPS branes

TL;DR

This paper explores string theory bouncing universe models driven by non-BPS D-branes, showing how tachyon dynamics can cause a bounce that connects contracting and expanding phases, with potential singularity resolution.

Contribution

It introduces new bouncing universe solutions involving non-BPS D-branes and analyzes their behavior using effective string theory actions, including effects of dilaton potentials.

Findings

Bounce driven by tachyon dynamics of non-BPS branes

Solutions interpolate between contracting and expanding phases

Adding dilaton potential can remove singularities

Abstract

We describe string frame bouncing universe scenarios involving the creation and annihilation of a non-BPS D9-brane in type IIA superstring theory. We find several classes of solutions, in which the bounce is driven by the tachyon dynamics of the non-BPS brane. The metric and the dilaton are consistently described in terms of the lowest order effective action. The bounce solutions interpolate between contracting and expanding pre-big bang (or post-big bang) solutions. The singular behavior of our bounce solutions is the same as that of the pre-big bang (or post-big bang) solution. Upon adding a simple dilaton potential the asymptotic curvature singularity is removed but the dilaton still grows without bound. Such a potential may result from $\alpha'$ corrections in the open string sector.