Brane cosmology and Kaluza–Klein gravitinos

Abstract

The cosmology of Kaluza–Klein (KK) gravitinos in models with extra dimensions is considered.The main result is that the production of such KK modes is not compatible with an epochof non-standard expansion after inflation. This is so because the big bang nucleosynthesis(BBN) constraint on the zero mode forces the reduced five-dimensional Planck massM5 down to values much smaller than the usual four-dimensional one yields,but this in turn implies that many KK states are available for a giventemperature. Once these states are taken into account one finds that there is noM5 for which the KK gravitinos produced satisfy BBN and overclosure constraints. Thisconclusion holds for both flat and warped models in which only gravity propagates in thefull spacetime.