The Spatial Clustering of Primordial Black Holes
  The possibility that primordial black holes (PBHs) are the dark matter (or a
fraction thereof) has attracted much attention recently. Their spatial
clustering is a fundamental property which determines, among others, whether
current observational constraints are evaded within a given mass range, whether
merging is significant and whether primordial black holes could generate
cosmological structure. We treat them as discrete objects and clarify the issue
of their spatial clustering, with an emphasis on short-range exclusion and its
impact on their large scale power spectrum. Even if a Poissonian self-pair term
is always present in the zero-lag correlation, this does not necessarily imply
that primordial black holes are initially Poisson distributed. However, while
the initial PBH clustering depends on the detailed shape of the small-scale
power spectrum, we argue that it is not relevant for a narrow spectral feature
and primordial black hole masses still allowed by observations.
