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arXiv · 2501.11337

Spectrum of third-order tensor perturbations induced by excited scalar fields

Cheng-Jun Fang·Zhi-Zhang Peng·Han-Wen Hu·Zong-Kuan Guo
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Abstract

We calculate for the first time the third-order spectrum of gravitational waves sourced by the amplified scalar field perturbations during inflation using the in-in formalism, and discuss the conditions for the third-order spectrum to be smaller than the second-order one. Assuming an exponential growth of the sub-horizon modes of the scalar field perturbations, we find that the third-order spectrum increases faster than the second-order one as the amplification of the field perturbations increases, and thus the third-order spectrum dominates for detectable gravitational waves, which indicates that the perturbation theory breakdowns.

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Cheng-Jun Fang, Zhi-Zhang Peng, Han-Wen Hu, Zong-Kuan Guo. 2025-01-20. Spectrum of third-order tensor perturbations induced by excited scalar fields. https://doi.org/10.1103/physrevd.111.103508

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