Primordial black holes from long-range scalar forces and scalar
  radiative cooling
  We describe a new scenario for the formation of primordial black holes
(PBHs). In the early Universe, the long-range forces mediated by the scalar
fields can lead to formation of halos of heavy particles even during the
radiation-dominated era. The same interactions result in the emission of scalar
radiation from the motion and close encounters of particles in such halos.
Radiative cooling due the scalar radiation allows the halos to collapse to
black holes. We illustrate this scenario on a simple model with fermions
interacting via the Yukawa forces. The abundance and the mass function of PBHs
are suitable to account for all dark matter, or for some gravitational wave
events detected by LIGO. The model relates the mass of the dark-sector
particles to the masses and abundance of dark matter PBHs in a way that can
explain why the dark matter and the ordinary matter have similar mass
densities. The model also predicts a small contribution to the number of
effective light degrees of freedom, which can help reconcile different
measurements of the Hubble constant.
