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arXiv · 2511.22949

Collapse of Axion Domain Wall Induced by Helical Primordial Magnetic Fields

Zizhuo Zhao·Yuefeng Di·Ligong Bian·Jing Shu
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Abstract

Stable domain wall (DW) must decay to avoid overclose the Universe. A commonly used solution is to slightly break the PQ symmetry by introducing a bias term in the potential. In this work, we propose an alternative, symmetry-preserving mechanism: coupling the axion field to a helical primordial magnetic field (PMF) via the Chern-Simons term. Using three-dimensional lattice simulations, we evolve the DW network and demonstrate that it can successfully drive DW decay. Our quantitative results further show that the correlation length of the PMF plays a crucial role in determining the decay rate of the DW network and the resulting axion and gravitational wave radiation.

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Zizhuo Zhao, Yuefeng Di, Ligong Bian, Jing Shu. 2025-11-28. Collapse of Axion Domain Wall Induced by Helical Primordial Magnetic Fields. https://arxiv.org/abs/2511.22949

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