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 spike-like structure. In contrast to
models in which PBHs produced from overdense regions, our model avoids the
uncertainties of PBHs production mechanism. PBHs from domain walls with mass
around $10^{20}\mathrm{g}$ may constitute all dark matter, those with mass
around $10^{34}\mathrm{g}$ can explain the merger events of binary black holes
detected by LIGO.
