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New test of modified gravity with gravitational wave experiments

Marisol Jimenez Cruz, Flavio C. Sánchez Orcid Logo, Gianmassimo Tasinato Orcid Logo

Physical Review D, Volume: 113, Issue: 4

Swansea University Authors: Marisol Jimenez Cruz, Gianmassimo Tasinato Orcid Logo

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DOI (Published version): 10.1103/wy1k-f8bn

Abstract

We propose a new strategy to probe nontensorial polarizations in the stochastic gravitational wave (GW) background. Averaging over polarization angles, we find that three-point correlations of the GW signal vanish for tensor and vector modes, while scalar modes generically leave a nonzero imprint. T...

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Published in: Physical Review D
ISSN: 2470-0010 2470-0029
Published: American Physical Society (APS) 2026
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URI: https://cronfa.swan.ac.uk/Record/cronfa71365
Abstract: We propose a new strategy to probe nontensorial polarizations in the stochastic gravitational wave (GW) background. Averaging over polarization angles, we find that three-point correlations of the GW signal vanish for tensor and vector modes, while scalar modes generically leave a nonzero imprint. This property makes the GW bispectrum a distinctive and robust diagnostic of scalar polarizations predicted in theories beyond general relativity. We derive the corresponding response functions for ground-based interferometers, pulsar timing arrays, and astrometric observables, and we construct an optimal estimator together with simple Fisher forecasts for pulsar timing sensitivity. As a proof of principle, we show that second-order GWs sourced by primordial magnetogenesis can be characterized by large three-point functions. Our results demonstrate that GW three-point correlations provide a novel observational window on physics beyond general relativity.
College: Faculty of Science and Engineering
Funders: We are partially funded by the STFC Grants No. ST/T000813/1 and No. ST/X000648/1.
Issue: 4