Glimmers from the axiverse

We study axion-photon couplings in compactifications of type IIB string theory. We find that these couplings are systematically suppressed compared to the inverse axion periodicity, as a result of two effects. First, couplings to the QED theta angle are suppressed for axion mass eigenstates that are...

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Bibliographic Details
Published in:Journal of cosmology and astroparticle physics 2024-09, Vol.2024 (9), p.71
Main Authors: Gendler, Naomi, Marsh, David J.E., McAllister, Liam, Moritz, Jakob
Format: Article
Language:English
Subjects:
axions
Birefringence
Couplings
dark energy theory
Hypothetical particles
Instantons
Phenomenology
Photons
Quantum electrodynamics
quantum gravity phenomenology
String theory
string theory and cosmology
X ray spectra
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Summary:We study axion-photon couplings in compactifications of type IIB string theory. We find that these couplings are systematically suppressed compared to the inverse axion periodicity, as a result of two effects. First, couplings to the QED theta angle are suppressed for axion mass eigenstates that are light compared to the mass scale set by stringy instantons on the cycle supporting QED. Second, in compactifications with many axions the intersection matrix is sparse, making kinetic mixing weak. We study the resulting phenomenology in an ensemble of 200,000 toy models constructed from the Kreuzer-Skarke database up to the maximum Hodge number h 1,1 = 491. We examine freeze-in production and decay of thermal axions, birefringence of the cosmic microwave background, X-ray spectrum oscillations, and constraints on the QCD axion from supernovae. We conclude that compactifications in this corner of the landscape involve many invisible axions, as well as a handful that may be detectable via photon couplings.
ISSN:1475-7516
1475-7516
DOI:10.1088/1475-7516/2024/09/071