Light to Heavy, Brief to Eternal: An Axion for Every Occasion (in the Early Universe)

Fuente: arXiv
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Autor principal: D'Eramo, Francesco
Formato: Preprint
Publicado: 2026
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author D'Eramo, Francesco
author_facet D'Eramo, Francesco
contents The early universe grants access to energy scales far beyond those achievable in terrestrial experiments and allows unstable Standard Model particles to play an active dynamical role. In this contribution, we focus on recent studies aimed at quantifying the potential of the early universe to probe the properties and interactions of axions. The discussion is organized around four classes of axion scenarios, ordered from long to short lifetimes: (i) stable or long-lived axions contributing to dark radiation; (ii) stable or long-lived axions produced out-of-equilibrium and constituting dark matter; (iii) metastable axions whose decays inject energy into the primordial plasma and leave observable signatures in the global 21 cm signal; and (iv) very short-lived axions that act only as portals to additional degrees of freedom. Together, these scenarios highlight the interplay between axion phenomenology and early universe cosmology and demonstrate the potential of cosmological data to probe axions over a broad range of masses and lifetimes.
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institution arXiv
publishDate 2026
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spellingShingle Light to Heavy, Brief to Eternal: An Axion for Every Occasion (in the Early Universe)
D'Eramo, Francesco
High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
The early universe grants access to energy scales far beyond those achievable in terrestrial experiments and allows unstable Standard Model particles to play an active dynamical role. In this contribution, we focus on recent studies aimed at quantifying the potential of the early universe to probe the properties and interactions of axions. The discussion is organized around four classes of axion scenarios, ordered from long to short lifetimes: (i) stable or long-lived axions contributing to dark radiation; (ii) stable or long-lived axions produced out-of-equilibrium and constituting dark matter; (iii) metastable axions whose decays inject energy into the primordial plasma and leave observable signatures in the global 21 cm signal; and (iv) very short-lived axions that act only as portals to additional degrees of freedom. Together, these scenarios highlight the interplay between axion phenomenology and early universe cosmology and demonstrate the potential of cosmological data to probe axions over a broad range of masses and lifetimes.
title Light to Heavy, Brief to Eternal: An Axion for Every Occasion (in the Early Universe)
topic High Energy Physics - Phenomenology
Cosmology and Nongalactic Astrophysics
url https://arxiv.org/abs/2602.11121