Cosmology of the companion-axion model: dark matter, gravitational waves, and primordial black holes

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Autori principali: Chen, Zhe, Kobakhidze, Archil, O'Hare, Ciaran A. J., Picker, Zachary S. C., Pierobon, Giovanni
Natura: Preprint
Pubblicazione: 2021
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author Chen, Zhe
Kobakhidze, Archil
O'Hare, Ciaran A. J.
Picker, Zachary S. C.
Pierobon, Giovanni
author_facet Chen, Zhe
Kobakhidze, Archil
O'Hare, Ciaran A. J.
Picker, Zachary S. C.
Pierobon, Giovanni
contents The companion-axion model introduces a second QCD axion to rescue the Peccei-Quinn solution to the strong-CP problem from the effects of colored gravitational instantons. As in single-axion models, the two axions predicted by the companion-axion model are attractive candidates for dark matter. The model is defined by two free parameters, the scales of the two axions' symmetry breaking, so we can classify production scenarios in terms of the relative sizes of these two scales with respect to the scale of inflation. We study the cosmological production of companion-axion dark matter in order to predict windows of preferred axion masses, and calculate the relative abundances of the two particles. Additionally, we show that the presence of a second axion solves the cosmological domain wall problem automatically in the scenarios in which one or both of the axions are post-inflationary. We also suggest unique cosmological signatures of the companion-axion model, such as the production of a $\sim$10 nHz gravitational wave background, and $\sim 100\,M_\odot$ primordial black holes.
format Preprint
id arxiv_https___arxiv_org_abs_2110_11014
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle Cosmology of the companion-axion model: dark matter, gravitational waves, and primordial black holes
Chen, Zhe
Kobakhidze, Archil
O'Hare, Ciaran A. J.
Picker, Zachary S. C.
Pierobon, Giovanni
High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
The companion-axion model introduces a second QCD axion to rescue the Peccei-Quinn solution to the strong-CP problem from the effects of colored gravitational instantons. As in single-axion models, the two axions predicted by the companion-axion model are attractive candidates for dark matter. The model is defined by two free parameters, the scales of the two axions' symmetry breaking, so we can classify production scenarios in terms of the relative sizes of these two scales with respect to the scale of inflation. We study the cosmological production of companion-axion dark matter in order to predict windows of preferred axion masses, and calculate the relative abundances of the two particles. Additionally, we show that the presence of a second axion solves the cosmological domain wall problem automatically in the scenarios in which one or both of the axions are post-inflationary. We also suggest unique cosmological signatures of the companion-axion model, such as the production of a $\sim$10 nHz gravitational wave background, and $\sim 100\,M_\odot$ primordial black holes.
title Cosmology of the companion-axion model: dark matter, gravitational waves, and primordial black holes
topic High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Theory
url https://arxiv.org/abs/2110.11014