New test of modified gravity with gravitational wave experiments

2025/09/10 by Norman Cruz, Cruz, N. M. Jiménez, Flavio C. Sánchez +3
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Noncommutative and Quantum Gravity Theories #Pulsars and Gravitational Waves Research

paper · pdf · doi:10.48550/arxiv.2509.08273

openalex publication_date 2025/09/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We propose a new strategy to probe non-tensorial 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.

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Related

• Detecting Parity-Violating Gravitational Wave Backgrounds with Pulsar Polarization Arrays
• A Test of Gravity with Pulsar Timing Arrays
• Constraining primordial non-Gaussianity and parity-violation through Scalar-Induced Gravitational Waves with next-generation ground-based interferometers
• Testing the polarization of gravitational wave background with LISA-TianQin network
• Prospects for detecting anisotropies and polarization of the stochastic gravitational wave background with ground-based detectors