Formation of primordial black holes after Starobinsky inflation

In this paper, we adapted the Appleby-Battye-Starobinsky model of F(R) gravity towards describing double cosmological inflation and formation of primordial black holes with masses up to 10(19) g in the single-field model. We found that it is possible to get an enhancement of the power spectrum of scalar curvature perturbations to the level beyond the Hawking (black hole evaporation) limit of 10(15) g, so that the primordial black holes resulting from gravitational collapse of those large primordial perturbations can survive in the present universe and form part of cold dark matter. Our results agree with the current measurements of cosmic microwave background radiation within 3 sigma but require fine-tuning of the parameters.