Journal Club - An Eikonal Approach to Gravitational Scattering and Waveforms - Carlo Heissenberg

Title: An Eikonal Approach to Gravitational Scattering and Waveforms

Abstract: In this talk, I will discuss some recent developments in the calculation of the gravitational waveform emitted during a scattering of two compact objects, considering two complementary regimes. The first is the post-Minkowskian (PM) approximation, where one focuses on widely separated objects, i.e. scatterings at large impact parameters. In this setup, interactions are weak and can be treated perturbatively. A particularly natural approach to attack this problem is to exploit the connection with scattering amplitudes, for which the eikonal framework offers a systematic way to describe the classical limit. I will discuss in particular how the next-to-leading PM waveform can be extracted from a one-loop 2-to-3 amplitude. The second approximation consists in focusing on low-frequency emissions, which are governed by universal soft theorems. These are simple relations that dictate in particular the structure of leading log-enhanced pieces of the type \omega^{n-1}(\log\omega)^n for n=0,1,2... in the low-frequency expansion, as \omega \to 0. I will present a recent proposal for a resummation of all such terms and discuss their contribution to the energy and angular momentum emission spectrum.