Ruling out light axions: the writing is on the wall

Abstract

We revisit the domain wall problem for QCD axion models with more than one quark charged under the Peccei-Quinn symmetry. Symmetry breaking during or after inflation results in the formation of a domain wall network which would cause cosmic catastrophe if it comes to dominate the Universe. The network may be made unstable by invoking a `tilt' in the axion potential due to Planck scale suppressed non-renormalisable operators. Alternatively the random walk of the axion field during inflation can generate a `bias' favouring one of the degenerate vacua, but we find that this mechanism is in practice irrelevant. Consideration of the axion abundance generated by the decay of the wall network then requires the Peccei-Quinn scale to be rather low -- thus ruling out e.g. the DFSZ axion with mass below 11 meV, where most experimental searches are in fact focussed.

22 pages, 4 figures; Updated with additional citations, clarifications & comments - conclusion essentially unchanged

References in corpus (11)

• An Improved Experimental Limit on the Electric Dipole Moment of the Neutron
• Measurement of the permanent electric dipole moment of the neutron
• Physics potential of the International Axion Observatory (IAXO)
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• Redefining the Axion Window
• Stellar Recipes for Axion Hunters
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Cited by in corpus (11)

• First search for axion dark matter with a Madmax prototype
• Induced Domain Walls of QCD Axion, and Gravitational Waves
• The Quality/Cosmology Tension for a Post-Inflation QCD Axion
• The Flavor of QCD Axion Dark Matter
• A Common Origin for the QCD Axion and Sterile Neutrinos from $SU(5)$ Strong Dynamics
• Bounds on heavy axions with an X-ray free electron laser
• Imperfect Axion Precludes the Domain Wall Problem
• Inflation and Higgs Phenomenology in a Model Unifying the DFSZ Axion with the Majoron
• Resolving the QCD Axion Domain Wall Problem with a Light Axion
• How Viable Is a QCD Axion near 10 MeV?
• Exploring the viability of pseudo Nambu-Goldstone boson as ultralight dark matter in a mass range relevant for strong gravity applications