Cosmology with bulk viscosity and the gravitino problem
  The gravitino problem is revisited in the framework of cosmological models in
which the primordial cosmic matter is described by a relativistic imperfect
fluid. Dissipative effects (or bulk viscosity effects) arise owing to the
different cooling rates of the fluid components. We show that the effects of
the bulk viscosity allow to avoid the late abundance of gravitinos. In
particular, we found that for a particular choice of the parameters
characterizing the cosmological model, the gravitino abundance turns out to be
independent on the reheating temperature.
