Gravitational Waves from Reheating beyond Instantaneous Thermalization
Abstract
We study gravitational-wave production during perturbative reheating without assuming instantaneous thermalization of the inflaton decay products. The injected energetic particles thermalize through an in-medium cascade of nearly collinear splittings subject to the Landau-Pomeranchuk-Migdal effect and are ultimately isotropized by elastic scatterings near the thermal scale. The non-thermal hard population present before complete thermalization produces an additional gravitational-wave component through hard-soft scatterings, with ΩGW∝ f1/2 below the injection-scale turnover. The same isotropization erases the directional information underlying the vacuum 1/k bremsstrahlung soft pole, changing the deep-infrared spectrum from ΩGW∝ f to ΩGW∝ f3.
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BibTeX
@misc{mukaida2026gravitational,
title = {{Gravitational Waves from Reheating beyond Instantaneous Thermalization}},
author = {Kyohei Mukaida and Tenta Tsuji},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01480},
eprint = {2609.01480},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.01480},
}
RIS
TY - UNPB
TI - Gravitational Waves from Reheating beyond Instantaneous Thermalization
AU - Kyohei Mukaida
AU - Tenta Tsuji
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.01480
UR - https://arxiv.org/abs/2609.01480
AB - We study gravitational-wave production during perturbative reheating without assuming instantaneous thermalization of the inflaton decay products. The injected energetic particles thermalize through an in-medium cascade of nearly collinear splittings subject to the Landau-Pomeranchuk-Migdal effect and are ultimately isotropized by elastic scatterings near the thermal scale. The non-thermal hard population present before complete thermalization produces an additional gravitational-wave component through hard-soft scatterings, with Ω_GW∝ f^1/2 below the injection-scale turnover. The same isotropization erases the directional information underlying the vacuum 1/k bremsstrahlung soft pole, changing the deep-infrared spectrum from Ω_GW∝ f to Ω_GW∝ f^3.
ER -