The cosmology of decaying gravitinos

Abstract

We consider the cosmological constraints on unstable particles with masses O(mW). Constraints from the energy density during primordial nucleosynthesis, from subsequent entropy generation, and from perturbations of the microwave background are not as restrictive as bounds from the dissociation of light elements. Most restrictive is the need to avoid over-production of D and 3He through the photo-dissociation of 4He. When applied to gravitinos, this bound imposes an upper limit of O(108) GeV on the reheating temperature after inflation, which could create problems for baryosynthesis in supersymmetric theories. These problems can be avoided if the photino is heavier than the gravitino.