Imperfect axions with no domain wall problem

Marco Gorghetto; Edward Hardy; Gilad Perez; Stefan Stelzl

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arXiv · 2608.27553

Imperfect axions with no domain wall problem

Marco Gorghetto·Edward Hardy·Gilad Perez·Stefan Stelzl

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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.

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Marco Gorghetto, Edward Hardy, Gilad Perez, Stefan Stelzl. 2026-08-27. Imperfect axions with no domain wall problem. https://arxiv.org/abs/2608.27553

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