Stochastic gravitational waves from narrow-band cosmological magnetic fields
Abstract
We calculate the spectrum of gravitational waves generated by a cosmological magnetic field with a narrow-band power spectrum. For a spectrum narrowly peaked at a comoving wavenumber kc, we find that the gravitational wave signal peaks at 2kc and has a sharp cutoff at this scale. We apply this result to an ultralight dark matter model of magnetogenesis operating around recombination, in which an axion-photon coupling generates a helical magnetic field by parametric resonance. We determine the conditions for the resulting gravitational waves to enter the frequency range of pulsar timing experiments. Although the required frequency can be reached for sufficiently large coupling, the corresponding amplitude is below the experimental sensitivity for physically allowed energy densities of the magnetic field. We generalize this conclusion to models of magnetogenesis operating at other epochs, estimating as T ≃ 160 MeV the temperature of a magnetogenesis process assumed to be the source of the stochastic gravitational wave background suggested by pulsar timing arrays. We place the lower bound T ≳ 1-10 MeV on such viable models.
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BibTeX
@misc{aires2026stochastic,
title = {{Stochastic gravitational waves from narrow-band cosmological magnetic fields}},
author = {Abdias Aires and Tatsuya Daniel},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.12719},
eprint = {2610.12719},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.12719},
}
RIS
TY - UNPB
TI - Stochastic gravitational waves from narrow-band cosmological magnetic fields
AU - Abdias Aires
AU - Tatsuya Daniel
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.12719
UR - https://arxiv.org/abs/2610.12719
AB - We calculate the spectrum of gravitational waves generated by a cosmological magnetic field with a narrow-band power spectrum. For a spectrum narrowly peaked at a comoving wavenumber k_c, we find that the gravitational wave signal peaks at 2k_c and has a sharp cutoff at this scale. We apply this result to an ultralight dark matter model of magnetogenesis operating around recombination, in which an axion-photon coupling generates a helical magnetic field by parametric resonance. We determine the conditions for the resulting gravitational waves to enter the frequency range of pulsar timing experiments. Although the required frequency can be reached for sufficiently large coupling, the corresponding amplitude is below the experimental sensitivity for physically allowed energy densities of the magnetic field. We generalize this conclusion to models of magnetogenesis operating at other epochs, estimating as T ≃ 160 MeV the temperature of a magnetogenesis process assumed to be the source of the stochastic gravitational wave background suggested by pulsar timing arrays. We place the lower bound T ≳ 1-10 MeV on such viable models.
ER -