Primordial black holes from cosmic domain walls

We investigate the formation of primordial black holes (PBHs) from the collapse of spherically symmetric domain wall bubbles, which spontaneously nucleate via quantum tunneling during inflation. Since the tension of domain walls changes with time and so domain walls nucleate in a short time interval, the mass function of PBHs in general has a spikelike structure. In contrast to models in which PBHs are produced from overdense regions, our model avoids the uncertainties of the PBHs production mechanism. PBHs from domain walls with mass around 10^20 g may constitute all dark matter, and those with mass around 10^34 g can explain the merger events of binary black holes detected by LIGO.