Speaker: Hanlin Song (Peking University)
Abstract: The constancy of the gravitational constant $G$ is a cornerstone of the strong equivalence principle and of general relativity, yet its possible temporal variation remains a key target in tests of fundamental physics. Gravitational-wave (GW) astronomy, especially when combined with electromagnetic observations, provides a qualitatively new opportunity to probe this principle in the strong-field and dynamical regime.
In this work, we develop a GW waveform model with a slowly varying gravitational constant, incorporating its effects both on compact binary dynamics and GW propagation in an expanding universe. Applying this framework to the binary neutron star merger GW170817, together with independent electromagnetic constraints on the luminosity distance, sky localization and binary inclination from GRB 170817A, we perform a joint Bayesian analysis that disentangles varying-$G$ effects from astrophysical degeneracies.
We find no evidence for a temporal variation of the gravitational constant, and constrain its fractional time derivative to $\dot{G}/G \in [-3.36 \times 10^{-9}, 5.34\times10^{-10}]~{\rm yr^{-1}}$, representing the most stringent bounds obtained to date from real GW observations. Our results demonstrate the power of multi-messenger astronomy as a precision probe of the strong equivalence principle in the relativistic regime.
Time: 10:00-11:00, 2026-01-12
Location: R1710, SIMIS
Introduction to the Speaker: Hanlin Song is a PhD student at the Institute of Theoretical Physics, Peking University, under the supervision of Professor Bo-Qiang Ma. He received his bachelor’s degree in physics from Jilin University in 2021. His research focuses on experimental tests of fundamental physics, including probes for Lorentz invariance violation using gamma-ray burst observations, tests of modified gravity theories with gravitational-wave data, and the application of machine-learning techniques in gravitational-wave physics.
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