The GW190521 Mass Gap Event and the Primordial Black Hole Scenario
  The LIGO/Virgo Collaboration has recently observed GW190521, the first binary
black hole merger with at least the primary component mass in the mass gap
predicted by the pair-instability supernova theory. This observation disfavors
the standard stellar-origin formation scenario for the heavier black hole,
motivating alternative hypotheses. We show that GW190521 cannot be explained
within the Primordial Black Hole (PBH) scenario if PBHs do not accrete during
their cosmological evolution, since this would require an abundance which is
already in tension with current constraints. On the other hand, GW190521 may
have a primordial origin if PBHs accrete efficiently before the reionization
epoch.
