A New Solution to the Gravitino Problem:Suppressed Production by Sgoldstino Dynamics

In supersymmetric theories, the gravitino is copiously produced by the scattering of the thermal particles at the end of inflationary reheating. The gravitino is overproduced unless the reheat temperature is sufficiently low, which is incompatible with thermal leptogenesis. This is known as the gravitino problem. In models of low scale mediation, the field value of the sgoldstino determines the mediation scale. We point out that the sgoldstino field value can be different in the early Universe than the present one. In particular, a large initial field value since the era of the inflationary reheating suppresses the gravitino production significantly and removes the gravitino problem. We rigorously analyze the cosmological evolution of the sgoldstino and show that the reheat temperature may well exceed the conventional upper bound, restoring the compatibility with thermal leptogenesis.