Gravitational Waves from Post-Inflationary Magnetism: Direct and Scalar-Induced Contributions
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| Format: | Preprint |
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2026
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| _version_ | 1866914622700781568 |
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| author | Maiti, Subhasis |
| author_facet | Maiti, Subhasis |
| contents | We study stochastic gravitational waves generated in a post-inflationary magnetogenesis scenario with time-dependent gauge couplings during inflation and reheating. In this setup, magnetic anisotropic stress directly sources gravitational waves, while the induced curvature perturbations generate an additional scalar-induced GW component. We compare the spectral behavior of the two contributions and find that the magnetic component dominates the peak amplitude, whereas the scalar-induced contribution becomes important on larger scales. For blue magnetic spectra with $n_{\rm b}\geq3/2$, both spectra follow the universal infrared scaling $Ω_{\rm GW}(f\ll f_{\rm peak})\propto f^3$. However, their ultraviolet behaviors differ significantly for $f>f_{\rm peak}$, leading to distinct spectral features. For suitable reheating and magnetogenesis parameters, the resulting GW signal naturally extends into the nano-Hz range relevant for pulsar timing array observations, while remaining consistent with current bounds. The distinct spectral features of the two components may provide a useful probe of reheating dynamics and primordial magnetogenesis. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_24715 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Gravitational Waves from Post-Inflationary Magnetism: Direct and Scalar-Induced Contributions Maiti, Subhasis Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology We study stochastic gravitational waves generated in a post-inflationary magnetogenesis scenario with time-dependent gauge couplings during inflation and reheating. In this setup, magnetic anisotropic stress directly sources gravitational waves, while the induced curvature perturbations generate an additional scalar-induced GW component. We compare the spectral behavior of the two contributions and find that the magnetic component dominates the peak amplitude, whereas the scalar-induced contribution becomes important on larger scales. For blue magnetic spectra with $n_{\rm b}\geq3/2$, both spectra follow the universal infrared scaling $Ω_{\rm GW}(f\ll f_{\rm peak})\propto f^3$. However, their ultraviolet behaviors differ significantly for $f>f_{\rm peak}$, leading to distinct spectral features. For suitable reheating and magnetogenesis parameters, the resulting GW signal naturally extends into the nano-Hz range relevant for pulsar timing array observations, while remaining consistent with current bounds. The distinct spectral features of the two components may provide a useful probe of reheating dynamics and primordial magnetogenesis. |
| title | Gravitational Waves from Post-Inflationary Magnetism: Direct and Scalar-Induced Contributions |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2605.24715 |