Primordial Black Holes: Tunnelling vs. No Boundary Proposal
  In the inflationary era, black holes came into existence together with the universe through the quantum process of pair creation. We calculate the pair creation rate from the no boundary proposal for the wave function of the universe. Our results are physically sensible and fit in with other descriptions of pair creation. The tunnelling proposal, on the other hand, predicts a catastrophic instability of de Sitter space to the nucleation of large black holes, and cannot be maintained. 
Raphael Bousso and Stephen W. Hawking (DAMTP, Cambridge)