Blue spectra and induced formation of primordial black holes

We investigate the statistical properties of primordial black hole (PBH) formation in the very early Universe. We show that the high level of inhomogeneity of the early Universe leads to the formation of the first generation PBHs. This causes later the appearance of a dustlike phase of the cosmological expansion. We discuss here a new mechanism for the second generation of PBH formation during the dustlike phase. This mechanism is based on the coagulation process. We demonstrate that the blue power spectrum of initial adiabatic perturbations after inflation leads to overproduction of primordial black holes with 10⁹g<~M<~10¹⁵g if the power index is n>~1.2.