Pre-Big Bang scenario on self-T-dual bouncing branes

Abstract

We consider a new class of five-dimensional dilatonic actions which are invariant underT-duality transformations along three compact coordinates, provided that anappropriate potential is chosen. We show that the invariance remains when we adda boundary term corresponding to a moving 3-brane, and we study the effectsof the T-duality symmetry on the brane cosmological equations. We find thatT-duality transformations in the bulk induce scale factor duality on the brane,together with a change of sign of the pressure of the brane cosmological matter.However, in a remarkable analogy with the Pre-Big Bang scenario, the cosmologicalequations are unchanged. Finally, we propose a model where the dual phases areconnected through a scattering of the brane induced by an effective potential. Weshow how this model can realize a smooth, non-singular transition between apre-Big Bang superinflationary Universe and a post-Big Bang accelerating Universe.