NBIA Gravity Seminar: Riccardo Gonzo

Speaker: Riccardo Gonzo

Title: The on-shell space of scattering and bound classical observables

Abstract: We will show how scattering orbits can inform bound-orbit models, allowing to harness the power of the S-matrix to construct gravitational waveforms relevant for the dynamics of compact binary systems. First, I will derive the so-called radial action from the worldline formalism, focusing for simplicity on the probe limit in a Kerr background. Then, I will show that such radial action (and the S-matrix) is a natural generating functional of classical observables, which provide a direct analytic continuation between a novel on-shell basis of scattering (coordinate time delay, elapsed proper time and deflection angle) and bound (radial frequency, averaged redshift and periastron advance) observables. Including radiation, we will then derive a new surprising map between scattering and bound waveforms, which is inspired and confirmed by Post-Newtonian calculations with the standard time-domain multipoles. Finally, we will emphasize the need to resum the perturbative series and to study non-local-in-time effects to make contact with phenomenological waveforms.