Primordial Black Holes as a dark matter candidate
  The detection of gravitational waves from mergers of tens of Solar mass black
hole binaries has led to a surge in interest in Primordial Black Holes (PBHs)
as a dark matter candidate. We aim to provide a (relatively) concise overview
of the status of PBHs as a dark matter candidate, circa Summer 2020. First we
review the formation of PBHs in the early Universe, focusing mainly on PBHs
formed via the collapse of large density perturbations generated by inflation.
Then we review the various current and future constraints on the present day
abundance of PBHs. We conclude with a discussion of the key open questions in
this field.
