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ALP dark matter in a primordial black hole dominated universe

Bernal, Nicolás; Perez-Gonzalez, Yuber F.; Xu, Yong; Zapata, Óscar

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Nicolás Bernal

Yong Xu

Óscar Zapata


We investigate the phenomenological consequences of axionlike particle (ALP) dark matter with an early matter domination triggered by primordial black holes (PBHs). We focus on light BHs with masses smaller than ∼109 g which fully evaporate before big bang nucleosynthesis. We numerically solve the coupled Boltzmann equations, carefully taking the graybody factors and BH angular momentum into account. We find that the entropy injection from PBH evaporation dilutes the ALP relic abundance originally produced via the vacuum misalignment mechanism, opening the parameter space with larger scales fa or, equivalently, smaller ALP-photon couplings gaγ, within the reach of future detectors as ABRACADABRA, KLASH, ADMX, and DM-Radio. Moreover, the ALP minicluster masses can be several orders of magnitude larger if the early universe features an PBH dominated epoch. For the relativistic ALPs produced directly from Hawking radiation, we find that their contribution to the dark radiation is within the sensitivity of next generation cosmic microwave background experiments. For the sake of completeness, we also revisit the particular case of the QCD axion.


Bernal, N., Perez-Gonzalez, Y. F., Xu, Y., & Zapata, Ó. (2021). ALP dark matter in a primordial black hole dominated universe. Physical Review D, 104(12), Article 123536.

Journal Article Type Article
Acceptance Date Nov 16, 2021
Online Publication Date Dec 16, 2021
Publication Date 2021-12
Deposit Date Sep 16, 2022
Publicly Available Date Sep 16, 2022
Journal Physical Review D
Print ISSN 2470-0010
Electronic ISSN 2470-0029
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 104
Issue 12
Article Number 123536


Published Journal Article (885 Kb)

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Copyright Statement
Published by the American Physical Society under the terms of
the Creative Commons Attribution 4.0 International license.
Further distribution of this work must maintain attribution to
the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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