Thermal and non-thermal production of gravitinos in the early universe

The excessive production of gravitinos in the early universe destroys the s uccessful predictions of nucleosynthesis. The thermal generation of graviti nos after inflation leads to the bound on the reheating temperature, T-RH l ess than or similar to 10(9) GeV. However, it has been recently realized th at the non-thermal generation of gravitinos in the early universe can be ex tremely efficient and overcome the thermal production by several orders of magnitude, leading to much tighter constraints on the reheating temperature . In this paper, we first investigate some aspects of the thermal productio n of gravitinos, taking into account that in fact reheating is not instanta neous and inflation is likely to be followed by a prolonged stage of cohere nt oscillations of the inflaton field. We then proceed by further investiga ting the non-thermal generation of gravitinos, providing the necessary tool s to study this process in a generic time-dependent background with any num ber of superfields. We also present the first numerical results regarding t he non-thermal generation of gravitinos in particular supersymmetric models .