Moduli decays and gravitinos

Abstract

One proposed solution of the moduli problem of string cosmology requires that the moduli are quite heavy, their decays reheating the Universe to temperatures above the scale of nucleosynthesis. In many of these scenarios, the moduli are approximately supersymmetric; it is then crucial that the decays to gravitinos are helicity suppressed. In this paper, we discuss situations where these decays are, and are not, suppressed. We also comment on a possible gravitino problem from inflaton decay.