Primordial Black Holes as Dark Matter: Almost All or Almost Nothing

  title={Primordial Black Holes as Dark Matter: Almost All or Almost Nothing},
  author={Brian C. Lacki and John F. Beacom},
  journal={The Astrophysical Journal},
Primordial black holes (PBHs) are expected to accrete particle dark matter around them to form ultracompact minihalos (UCMHs), if the PBHs themselves are not most of the dark matter. We show that if most dark matter is a thermal relic, then the inner regions of UCMHs around PBHs are highly luminous sources of annihilation products. Flux constraints on gamma rays and neutrinos set strong abundance limits, improving previous limits by orders of magnitude. Assuming enough particle dark matter… 

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