Heating in brane inflation and hidden dark matter

Abstract

Towards the end of brane inflation, the brane pair annihilation produces massive closedstrings. The transfer of this energy to standard model (SM) open string modes depends onwhere the SM branes and the brane annihilation are located: in the bulk, in the samethroat, or in different throats. We find that, in all cases as long as the brane annihilationand the SM branes are not both in the bulk, the transfer of energy to start the hot bigbang epoch can be efficient enough to be compatible with big bang nucleosynthesis. Thesuppression of the abundance of the graviton and its Kaluza–Klein (KK) thermalrelics follows from the warped geometry in flux compactification. This worksout even in the scenarios where a long period of tunnelling is expected. In themulti-throat scenario, we find a dynamical mechanism of selecting a long throat asthe SM throat. We establish three new dark matter candidates: KK modes withspecific angular momentum in the SM throat, those in the brane annihilationthroat, and different matters generated by KK modes tunnelled to other throats.Since the latter two couple to the visible matter sector only through gravitonmediation, they behave as hidden dark matter. Hidden dark matter has novelimplications for the dark matter coincidence problem and the high energy cosmic rays.