Primordial black hole formation during slow reheating after inflation

We study the formation of primordial black holes (PBHs) in the early Universe during a period of slow reheating after inflation. We demonstrate how the PBH formation mechanism may change even before the end of the matter-dominated phase and calculate the expected PBH mass function. We find that there is a threshold for the variance of the density contrast, sigma(c) similar or equal to 0.05, below which the transition occurs even before reheating, with this having important consequences for the PBH mass function. We also show that there is a maximum cutoff for the PBH mass at around 100 M-circle dot, below which the subdominant radiation bath affects PBH production, making the scenario particularly interesting for the recent LIGO observations of black hole mergers.