Reheating after S-brane ekpyrosis

Abstract

In recent work, two of us proposed a nonsingular ekpyrotic cosmology making use of an S-brane which forms at the end of the phase of ekpyrotic contraction. This S-Brane mediates a transition between contraction and expansion. Gravitational waves passing through the S-brane acquire a roughly scale-invariant spectrum, and if the S-brane has zero shear, then a roughly scale-invariant spectrum of cosmological perturbatiions results. Here, we study the production of gauge field fluctuations driven by the decay of the S-brane, and we show that the reheating process via gauge field production will be efficient, leading to a radiation-dominated expanding phase.