Description
Abstract: The direct detection of gravitational waves has put the relativistic
two-body problem in the spotlight and stimulated progress in
perturbative approaches that provide analytic insight into its dynamics.
Two strategies that have been witnessing interesting developments to
this end are the ones based on scattering amplitudes, which apply to
binary scatterings at large impact parameter, and on black-hole
perturbation theory, which applies to extreme-mass-ratio binaries. In
this talk, I will discuss how these two methods play complementary
roles, and how they naturally feature differential equations that
determine the gravitational perturbations induced by scatterings of
black holes both far away, at null infinity, and close to the event
horizons. Such waveforms characterize in particular the amounts of
energy and angular momentum that are emitted and reabsorbed by the system.