Year: 2026
Type: preprint
Abstract: Gravitational radiation from the early Universe offers a powerful window into physics beyond the Standard Model (SM). In this paper, we investigate the low-frequency tail of gravitational radiation produced by the decay of massive particles. The energy spectrum in Minkowski space-time, $dE/dω$, exhibits two distinct regimes: a flat bremsstrahlung/memory spectrum above a characteristic cutoff frequency and a suppressed quadratic frequency scaling below it. The typical rate of momentum change of the decay products determines the cutoff frequency. We calculate $dE/dω$ in two independent but equivalent ways: using Weinberg's soft graviton theorem and by solving the equations of motion. This further establishes the connection between Weinberg's soft graviton theorem and the gravitational memory formula, which we generalize to incorporate the effects of final-state scattering. We then compute the cosmological stochastic gravitational energy spectrum $h^2Ω_{\rm h}$ generated by many particle decays in the early Universe. We demonstrate that $h^2Ω_{\rm h}$ exhibits linear scaling with frequency above the cutoff frequency, transitioning to cubic scaling below it. Our findings reveal a suppression of the low-frequency signal compared to a naive linear extrapolation, with implications for detection prospects. Our results also reveal the connection between bremsstrahlung and memory in the context of cosmological stochastic gravitational energy spectra from the early Universe.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, Strong, Centres de Recerca de Catalunya, European Commission, National Research Foundation, Ministry of Education, Culture, Sports, Science and Technology, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Danmarks Grundforskningsfond, Generalitat de Catalunya, Ministerio de Ciencia e Innovación, Janggen-Pöhn-Stiftung, Institut de Física d'Altes Energies, Japan Society for the Promotion of Science, Japan Science and Technology Agency, European Regional Development Fund, Agencia Estatal de Investigación
Awards: G1143606313, G1175115578, G1286236842, G1401168639, G1855990336, G1863003419, G2064873908, G2262748287, G2309174360, G2341298403, G24120701, G2462415295, G2517729222, G252646220, G2601397997, G2660406951, G2824685711, G294895050, G3005324705, G300979063, G3083819904, G3427743928, G3480869486, G3518538256, G3546882995, G3562095311, G3681454997, G3783267339, G3840207496, G4042783231, G410571670, G4228227490, G425668148, G42916606, G430777504, G4342989573, Disease risk under environmental change and biodiversity loss – causes and consequences, G451917667, G464105488, New Pathways Connecting Theory and Experiment, G4744355279, G4762216095, G5080475149, G5195188938, G523076202, G526230902, G5421974903, G5539308778, G5967599077, G6033112984, G638836682, G6526127349, G6603587382, G6656126374, 理研-バークレー 数理量子科学イニシアティブ, G6902702339, G7084143925, Explore the Memory of Gravity, G745419941, 古代説話における諸寺縁起の研究, G787121397, 北海道の火山灰地急斜面の地辷り, 崩壊の予知に関する研究, G7981279683, G8345352404, G8522095481, G8575141037, G969889393, G99296377
OpenAlex ID: W7204482786
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