Scalar-induced gravitational waves in spatially covariant gravity with two tensorial degrees of freedom
Abstract
We study scalar-induced gravitational waves (SIGWs) in a spatially covariant gravity model with two tensorial degrees of freedom, minimally coupled to a k-essence scalar field. For the parameter choice considered during radiation domination, the quadratic tensor action coincides with that of general relativity (GR). We derive the scalar transfer functions at finite σ≡ C2N̅ and in the large-|σ| limit. We then construct the source function of SIGWs. We further examine a cubic extrinsic-curvature interaction that modifies the source function of SIGWs without affecting the background or quadratic actions. We calculate the fractional energy density of SIGWs for monochromatic and log-normal primordial curvature power spectra. We find that, for the positive values of σ studied, finite-σ effects suppress the spectrum over a broad range of scales relative to the result in the σ→ ∞ limit. In this limit, the cubic interaction suppresses the spectrum at small wavenumbers and enhances it at larger wavenumbers. These results show that modified scalar dynamics and non-linear interactions can alter the fractional energy density of SIGWs even when the quadratic tensor action is identical to that of GR.
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BibTeX
@misc{feng2026scalarinduced,
title = {{Scalar-induced gravitational waves in spatially covariant gravity with two tensorial degrees of freedom}},
author = {Jia-Xi Feng and Yang Yu and Yan-Heng Yu and Xian Gao and Qing-Guo Huang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.39252},
eprint = {2610.39252},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.39252},
}
RIS
TY - UNPB
TI - Scalar-induced gravitational waves in spatially covariant gravity with two tensorial degrees of freedom
AU - Jia-Xi Feng
AU - Yang Yu
AU - Yan-Heng Yu
AU - Xian Gao
AU - Qing-Guo Huang
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.39252
UR - https://arxiv.org/abs/2610.39252
AB - We study scalar-induced gravitational waves (SIGWs) in a spatially covariant gravity model with two tensorial degrees of freedom, minimally coupled to a k-essence scalar field. For the parameter choice considered during radiation domination, the quadratic tensor action coincides with that of general relativity (GR). We derive the scalar transfer functions at finite σ≡ C_2N̅ and in the large-|σ| limit. We then construct the source function of SIGWs. We further examine a cubic extrinsic-curvature interaction that modifies the source function of SIGWs without affecting the background or quadratic actions. We calculate the fractional energy density of SIGWs for monochromatic and log-normal primordial curvature power spectra. We find that, for the positive values of σ studied, finite-σ effects suppress the spectrum over a broad range of scales relative to the result in the σ→ ∞ limit. In this limit, the cubic interaction suppresses the spectrum at small wavenumbers and enhances it at larger wavenumbers. These results show that modified scalar dynamics and non-linear interactions can alter the fractional energy density of SIGWs even when the quadratic tensor action is identical to that of GR.
ER -