On-shell approach to spinning binaries in GR and beyond

by Panagiotis Marinellis

Tuesday 20 May 2025, 12:00 → 13:00 Europe/Madrid

IFAE Seminar Room (In-Person)

The detection of gravitational waves by the LIGO-VIRGO collaboration has marked a transformative era in astronomy, providing groundbreaking insights into the cosmos and creating new pathways for exploration. At the same time, advancements in the classical limit of quantum scattering amplitudes, particularly through the KMOC formalism, have enriched our understanding of compact binary systems.

 

In this talk, we will discuss the application of these techniques to scalar-tensor theories of gravity, where long range interactions are mediated by a massless scalar in addition to the graviton. Such theories include the Einstein-scalar-Gauss-Bonnet and Dynamical Chern-Simons theories and are of both theoretical and phenomenological interest.

We will start by providing an overview of how amplitude techniques are used to derive predictions for gravitational waves from binary systems of black holes and neutron stars. We will then proceed to give a purely "on-shell" description of arbitrarily spinning bodies with and without scalar hair, an effect which is often present in these theories and can lead to important modifications in the gravitational wave signal. We will discuss how all the required amplitudes can be calculated in a straightforward manner by using the on-shell and spinor-helicity techniques, which can be in turn used to directly compute waveforms for spinning binary systems. Finally, we will briefly discuss potential UV completions of these models, treating them as Effective Field Theories and leveraging modern amplitude methods for further insight.