Dynamical Tidal Response of Neutron Stars from Scattering Amplitudes

par Muddu Venkata Sai Saketh (International Centre for Theoretical Sciences (ICTS-TIFR), Bengaluru, India)

mercredi 30 sept. 2026, 14:45 → 16:00 Europe/Paris

Amphithéâtre Léon Motchane (IHES)

Séminaire Amplitudes et Gravitation sur l'Yvette (IHES/IPhT)

In this talk I will describe an amplitude-based framework for extracting the frequency-dependent tidal response of neutron stars while preserving the tidal resonances associated with their normal modes. The response is obtained by matching the amplitude for gravitational-wave scattering off a neutron star, equivalently gravitational Compton scattering, computed using relativistic stellar perturbation theory, to the corresponding amplitude in worldline effective field theory. The tidal contribution is isolated through the difference between the neutron-star and black-hole scattering phases. Unlike conventional treatments, the construction allows for a post-Newtonian expansion without Taylor expanding the response in frequency or assuming a harmonic-oscillator model for the internal dynamics.

I will present the tidal response through relative third post-Newtonian (3PN) order and use currently available numerical results to illustrate its frequency dependence. The results reproduce the known static Love numbers in the low-frequency limit, exhibit resonances at the expected stellar mode frequencies, and capture their damping through gravitational-wave emission. I will also discuss the renormalisation of the tidal response required through 3PN order. Time permitting, I will outline how the resulting response can be incorporated into binary dynamics and ultimately into gravitational waveforms. 

 

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