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arXiv · 2401.09818

Probing the speed of scalar-induced gravitational waves with pulsar timing arrays

Zu-Cheng Chen·Jun Li·Lang Liu·Zhu Yi
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Abstract

Recently, several regional pulsar timing array collaborations, including CPTA, EPTA, PPTA, and NANOGrav, have individually reported compelling evidence for a stochastic signal at nanohertz frequencies. This signal originates potentially from scalar-induced gravitational waves associated with significant primordial curvature perturbations on small scales. In this letter, we employ data from the EPTA DR2, PPTA DR3, and NANOGrav 15-year data set, to explore the speed of scalar-induced gravitational waves using a comprehensive Bayesian analysis. Our results suggest that, to be consistent with pulsar timing array observations, the speed of scalar-induced gravitational waves should be $c_g \gtrsim 0.61$ at a $95\%$ credible interval for a lognormal power spectrum of curvature perturbations. Additionally, this constraint aligns with the prediction of general relativity that $c_g=1$ within a $90\%$ credible interval. Our findings underscore the capacity of pulsar timing arrays as a powerful tool for probing the speed of scalar-induced gravitational waves.

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Zu-Cheng Chen, Jun Li, Lang Liu, Zhu Yi. 2024-01-18. Probing the speed of scalar-induced gravitational waves with pulsar timing arrays. https://doi.org/10.1103/physrevd.109.l101302

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