Gravitino problem in f(R) cosmology

The gravitino problem is investigated in the framework of f(R) cosmology. Since in f(R) cosmology the expansion laws of the Universe are modified, as compared to the standard cosmology, it follows that also the thermal history of particles gets modified. We show that f(R) models allow to avoid the late abundance of gravitinos. In particular, we found that for an appropriate choice of the parameters characterizing the f(R) model, the gravitino abundance turns out to be independent of the reheating temperature