Primordial Black Holes as Dark Matter: Recent Developments

• Published in: Annual review of nuclear and particle science Vol. 70; no. 1; pp. 355 - 394
• Main Authors: Carr, Bernard, Kühnel, Florian
• Format: Journal Article
• Language: English
• Published: Annual Reviews 19-10-2020
• Subjects: black holes; cosmic structure; dark matter; gravitational waves
• ISSN: 0163-8998; 1545-4134
• DOI: 10.1146/annurev-nucl-050520-125911

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 with the standard cold dark matter scenario, and sufficiently large PBHs might provide seeds for the supermassive black holes in galactic nuclei. More exotically, the Planck-mass relics of PBH evaporations or stupendously large black holes bigger than 10
12
M
could provide an interesting dark component.