# Primordial Black Holes as Dark Matter Candidates

### Submission summary

 As Contributors: Florian Kühnel Arxiv Link: https://arxiv.org/abs/2110.02821v2 (pdf) Date accepted: 2021-11-24 Date submitted: 2021-11-16 11:27 Submitted by: Kühnel, Florian Submitted to: SciPost Physics Lecture Notes Academic field: Physics Specialties: Gravitation, Cosmology and Astroparticle Physics Approaches: Theoretical, Experimental, Computational, Phenomenological, Observational

### Abstract

We review the formation and evaporation of primordial black holes (PBHs) and their possible contribution to dark matter. Various constraints suggest they could only provide most of it in the mass windows $10^{17}$ - $10^{23}\,$g or $10$ - $10^{2}\,M_{\odot}$, with the last possibility perhaps being suggested by the LIGO/Virgo observations. However, PBHs could have important consequences even if they have a low cosmological density. Sufficiently large ones might generate cosmic structures and provide seeds for the supermassive black holes in galactic nuclei. Planck-mass relics of PBH evaporations or stupendously large black holes bigger than $10^{12}\,M_{\odot}$ could also be an interesting dark component.

Published as SciPost Phys. Lect. Notes 48 (2022)

### List of changes

Referee 1

The referee has requested no changes but we are very grateful for the kind comments.

Referee 2

The referee is correct that we should have given more credit to the Zeldovich & Novikov paper, which preceded the Hawking paper by four years. Their accretion calculation turned out to be wrong but the Hawking paper also turned out to be wrong because it assumed the PBHs would retain their charge. We have therefore expanded the discussion and removed the description of Hawking as the "father" of PBHs. We've also explained beta and corrected the typographical errors indicated.

Referee 3

This referee has clearly read the paper very carefully, pointing out many typos and undefined quantities, for which we are grateful. We've made all the associated corrections but we've not reacted to the final paragraph "Suggestions for possible improvements". Other lectures have surely explained the evidence for dark matter (point a) and we do mention Figs 5-8 briefly at the start of Section 3 (point b). Point c is very sensible but it would require an extra figure and a lot of work to provide this. We don't think we should modify Fig 11 (point d) because this is taken from another paper and does at least include the LIGO events.