Gravitino production in a thermal Universe revisited
  We study the production of spin 1/2 gravitinos in a thermal Universe. Taking
into account supersymmetry breaking due to the finite thermal energy density of
the Universe, there is a large enhancement in the cross section of production
of these gravitino states. We consider gravitinos with zero temperature masses
of 0.1 eV, 1 keV, 100 GeV and 30 TeV as representative of gauge mediated,
gravity mediated and anomaly mediated supersymmetry breaking scenarios. We find
that the abundance of gravitinos produced in the early Universe is very high
for gravitinos of mass 1 keV and 100 GeV. The gravitino abundances can be
sufficiently suppressed if the reheat temperature is less than 100 GeV and
$4\cdot 10^4$ gev respectively. However such low reheat temperatures will rule
out many models of baryogenesis including those via leptogenesis.
