A new mechanism for primordial black hole formation during reheating
  The Reheating process at the end of inflation is often modeled by an
oscillating scalar field which shows a background dust-like behaviour,
prompting the analysis of gravitational collapse and black hole formation in
this era to be approached by the spherical collapse of standard structure
formation. In the scalar field dark matter structure formation process
virialized halos halt the direct collapse, resulting in halos with condensed
central cores at the de Broglie scale of the dominant scalar field. We show
that a similar process can take place during reheating, leading to the
formation of primordial black holes (PBHs). We study the formation of PBHs
through the gravitational further collapse of structures virialized during
reheating, looking at the collapse of either the whole structure, or that of
the central core within these configurations. We compute the threshold
amplitude for the density contrast to undergo this process, for both free and
self-interacting scalar fields. We discuss the relevance of our results for the
abundance of PBHs at the lower end of the mass spectrum.
