Can Two-Point Correlations Determine Gravitational Waves from Sound Waves?
Abstract
Sound waves are expected to be a dominant source of gravitational waves (GWs) from cosmological first-order phase transitions. Their spectrum is commonly predicted using the fluid velocity two-point correlation function under the Gaussian approximation. However, since the GW source is quadratic in velocity, connected four-point correlations may also contribute to the GW spectrum. Through two analytical toy examples, we demonstrate that velocity two-point correlations alone does not always uniquely determine the GW spectrum. Moving beyond these idealized examples, we investigate a realistic acoustic source based on stochastic bubble nucleation and growth, proving that the connected contribution becomes subleading during subsequent linear acoustic propagation, although cosmic expansion limits this suppression. These results clarify when two-point reconstruction is reliable and how higher-order velocity correlations and the duration of acoustic emission affect GW predictions.
Related
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BibTeX
@misc{chen2026twopoint,
title = {{Can Two-Point Correlations Determine Gravitational Waves from Sound Waves?}},
author = {Guangshang Chen and Jianpeng Dai and Yang Xiao},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.07877},
eprint = {2611.07877},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.07877},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Can Two-Point Correlations Determine Gravitational Waves from Sound Waves?
AU - Guangshang Chen
AU - Jianpeng Dai
AU - Yang Xiao
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.07877
UR - https://arxiv.org/abs/2611.07877
AB - Sound waves are expected to be a dominant source of gravitational waves (GWs) from cosmological first-order phase transitions. Their spectrum is commonly predicted using the fluid velocity two-point correlation function under the Gaussian approximation. However, since the GW source is quadratic in velocity, connected four-point correlations may also contribute to the GW spectrum. Through two analytical toy examples, we demonstrate that velocity two-point correlations alone does not always uniquely determine the GW spectrum. Moving beyond these idealized examples, we investigate a realistic acoustic source based on stochastic bubble nucleation and growth, proving that the connected contribution becomes subleading during subsequent linear acoustic propagation, although cosmic expansion limits this suppression. These results clarify when two-point reconstruction is reliable and how higher-order velocity correlations and the duration of acoustic emission affect GW predictions.
ER -