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  • Open Access

New test of modified gravity with gravitational wave experiments

N. M. Jiménez Cruz1,*, Flavio C. Sánchez1,2,†, and Gianmassimo Tasinato1,3,‡

  • *Contact author: nmjc1209@gmail.com
  • †Contact author: flavio.sanchez@fisica.uaz.edu.mx
  • ‡Contact author: g.tasinato2208@gmail.com
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Phys. Rev. D 113, 044011 – Published 4 February, 2026

DOI: https://doi.org/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. 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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Phys. Rev. D 113, 044011– Published 4 February, 2026
  • Received 18 September 2025
  • Accepted 8 January 2026
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