Imperfect axions with no domain wall problem

Year: 2026

Type: preprint

Abstract: Post-inflationary axion theories with domain wall number $N>1$ suffer from a domain wall problem. We show analytically, and confirm via simulations, that there is a region of phenomenologically viable parameter space for such theories with additional PQ-violating operators. Contrary to the conventional picture, in such theories the beyond-QCD PQ violation destroys the axion strings before the QCD axion potential becomes cosmologically relevant. This regime is realized for axion decay constants $f_a \lesssim 10^{10} \, \rm GeV$, pointing to a QCD axion mass in the $10^{-3}-10^{-2}\,{\rm eV}$ range. The required additional PQ violation induces a neutron electric dipole moment within two orders of magnitude of the current experimental limit, placing it within the reach of upcoming neutron electric dipole moment experiments.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2608.27553

Authors: Gorghetto, Marco, Hardy, Edward, Perez, Gilad, Stelzl, Stefan

Institutions: Deutsches Elektronen-Synchrotron DESY, University of Oxford, Barcelona Institute of Science and Technology, Weizmann Institute of Science, Institute for High Energy Physics

Topic: Dark Matter and Cosmic Phenomena

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, Centres de Recerca de Catalunya, Deutsche Forschungsgemeinschaft, Generalitat de Catalunya, Israel Science Foundation, Ministerio de Ciencia e Innovación, Institut de Física d'Altes Energies, European Regional Development Fund, Agencia Estatal de Investigación, HORIZON EUROPE European Research Council

OpenAlex ID: W7204795375