Initial clustering and the primordial black hole merger rate
  If the primordial curvature perturbation followed a Gaussian distribution,
primordial black holes (PBHs) will be Poisson distributed with no additional
clustering. We consider local non-Gaussianity and its impact on the initial PBH
clustering and mass function due to mode coupling between long and short
wavelength modes. We show that even a small amount of non-Gaussianity results
in a significant enhancement on the PBH initial clustering and subsequent
merger rate and that the PBH mass function shifts to higher mass PBHs. However,
as the clustering becomes strong, the local number density of PBHs becomes
large, leading to a large theoretical uncertainty in the merger rate.
