Primordial Black Holes and Co-Decaying Dark Matter
  Models of Co-Decaying dark matter lead to an early matter dominated epoch --
prior to BBN -- which results in an enhancement of the growth of dark matter
substructure. If these primordial structures collapse further they can form
primordial black holes providing an additional dark matter candidate. We derive
the mass fraction in these black holes (which is not monochromatic) and
consider observational constraints on how much of the dark matter could be
comprised in these relics. We find that in many cases they can be a significant
fraction of the dark matter. Interestingly, the masses of these black holes can
be near the solar-mass range providing a new mechanism for producing black
holes like those recently detected by LIGO.
