ON THE THERMAL REGENERATION RATE FOR LIGHT GRAVITINOS IN THE EARLY UNIVERSE

We investigate the light gravitino regeneration rate in the early Univ erse in models based on N = 1 supergravity. Motivated by a recent clai m by Fischler, we evaluate finite-temperature effects on the gravitino regeneration rate due to the hot primordial plasma for a wide range o f the supersymmetry-breaking scale F. We find that the leading thermal corrections to the gravitino pole mass and to the Goldstino coupling are negligible for a wide range of temperatures, thereby justifying th e extension of the equivalence theorem for the helicity-1/2 gravitino and Goldstino to a hot primordial plasma background. Utilizing the Bra aten-Pisarski resummation method, and assuming that the other particle s are close to thermal equilibrium, the helicity-1/2 gravitino regener ation rate is found to be insensitive to magnetic Debye screening and of order alpha(s)(T) /F\T-2(3)(1+alpha(s)(T)log(1/alpha(s)(T))+T-2/\f\ ) up to a calculable, model-dependent O(1) numerical factor. We review the implications of this regeneration rate for supergravity cosmology , focusing in particular on scenarios for baryogenesis.