Cosmological simulation of axion-Higgs strings: Gravitational waves and dark matter

Abstract

Axions have long been considered plausible candidates for dark matter. The axion dark matter emitted from cosmic strings after the Peccei-Quinn (PQ) symmetry breaking in the early Universe was extensively simulated. In this work, we study dark matter and gravitational waves through the lattice simulation of the axion-Higgs string. We gave the dark matter overproduction and the big bang nucleosynthesis bounds on the axion decay constant fa and the axion mass ma for axionlike particles, and found that the predicted gravitational wave spectra cannot be probed by the dataset of the current pulsar timing array experiments. Published by the American Physical Society 2025