Stellar mass primordial black holes as cold dark matter

Primordial black holes (PBHs) might have formed in the early Universe due to the collapse of density fluctuations. PBHs may act as the sources for some of the gravitational waves recently observed. We explored the formation scenarios of PBHs of stellar mass, taking into account the possible influence of the QCD phase transition, for which we considered three different models: crossover model, bag model, and lattice fit model. For the fluctuations, we considered a running-tilt power-law spectrum; when these cross the ∼10^-9-10^-1 s Universe horizon they originate 0.05-500 M_⊙ PBHs that could (I) provide a population of stellar mass PBHs similar to the ones present on the binaries associated with all-known gravitational wave sources and (II) constitute a broad-mass spectrum accounting for ${\sim}76{{\ \rm per\ cent}}$ of all cold dark matter in the Universe.