Primordial Black Holes as Dark Matter: Recent Developments

Although the dark matter is usually assumed to be made up of some form of elementary particle, primordial black holes (PBHs) could also provide some of it. However, various constraints restrict the possible mass windows to 10 16 –10 17 g, 10 20 –10 24 g, and 10–10 3 M ⊙ . The last possibility is contentious but of special interest in view of the recent detection of black hole mergers by LIGO/Virgo. PBHs might have important consequences and resolve various cosmological conundra even if they account for only a small fraction of the dark matter density. In particular, those larger than 10 3 M ⊙ could generate cosmological structures through the seed or Poisson effect, thereby alleviating some problems associated…