The Astro-Primordial Black Hole Merger Rates: a Reappraisal
  Mainly motivated by the recent GW190521 mass gap event which we take as a
benchmark point, we critically assess if binaries made of a primordial black
hole and a black hole of astrophysical origin may form, merge in stellar
clusters and reproduce the LIGO/Virgo detection rate. While two previously
studied mechanisms -- the direct capture and the three body induced -- seem to
be inefficient, we propose a new "catalysis" channel based on the idea that a
subsequent chain of single-binary and binary-binary exchanges may lead to the
formation of a high mass binary pairs and show that it may explain the recent
GW190521 event if the local overdensity of primordial black holes in the
globular cluster is larger than a few.
