Heating in brane inflation and hidden dark matter

Towards the end of brane inflation, the brane pair annihilation produces massive closed strings. The transfer of this energy to standard model (SM) open string modes depends on where the SM branes and the brane annihilation are located: in the bulk, in the same throat, or in different throats. We find that, in all cases as long as the brane annihilation and the SM branes are not both in the bulk, the transfer of energy to start the hot big bang epoch can be efficient enough to be compatible with big bang nucleosynthesis. The suppression of the abundance of the graviton and its Kaluza-Klein (KK) thermal relics follows from the warped geometry influx compactification. This works out even in the scenarios where a long period of tunnelling is expected. In the multithroat scenario, we find a dynamical mechanism of selecting a long throat as the SM throat. We establish three new dark matter candidates: KK modes with specific angular momentum in the SM throat, those in the brane annihilation throat, and different matters generated by KK modes tunnelled to other throats. Since the latter two couple to the visible matter sector only through graviton mediation, they behave as hidden dark matter. Hidden dark matter has novel implications for the dark matter coincidence problem and the high energy cosmic rays.