Primordial black holes as a dark matter candidate

Abstract

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, focussing 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.

Effects of the shape of curvature peaks on the size of primordial black holes

“…(4) and Fig. (6), where we have compared the analytically computed bound of the ratio with its numerical calculation.…”

BlackHawk: A tool for computing Black Hole evaporation

“…A lot of effort has been put into the computation of the greybody factors for Schwarzschild (nonrotating, uncharged) and Kerr (rotating, uncharged) BHs, which are per se interesting results. These 6) and (7). Taken from [15].…”

“…There is a never-ending discussion about their origin: most, or at least some of them may be primordial. Many astrophysical constraints limit the fraction of DM that PBHs could represent, see for example [6] and references therein for a long review, and [7] for a more concise one. Recent work focuses on the nature of LIGO/Virgo BHs and the discrimination between the primordial and stellar origin using mass distribution or spin measurements [8][9][10][11][12][13][14].…”

“…Figure 1: Evolution of a BH mass (solid) and spin (dashed) following Eqs. (6) and(7). Taken from[15].…”

Primordial black holes and their formation

“…The power spectrum at the small scales relevant for PBHs formation must become orders of magnitude larger than detected on large scales via the CMB (Akrami et al 2020) which is a matter of active research. Since the amplitude of the power spectrum is only logarithmically sensitive to the PBHs abundance during the radiation domination, this variation has little to do with the different PBH masses (Green & Kavanagh 2020). However, the PBH mass distribution differs when using different theoretical techniques for their formation.…”