title: Understanding the "antikick" in the merger of binary black holes.
abstract: The generation of a large recoil velocity from the inspiral and merger of binary black holes represents one of the most exciting results of numerical-relativity calculations. While many aspects of this process have been investigated and explained, the "antikick," namely, the sudden deceleration after the merger, has not yet found a simple explanation. We show that the antikick can be understood in terms of the radiation from a deformed black hole where the anisotropic curvature distribution on the horizon correlates with the direction and intensity of the recoil. Our analysis is focused on Robinson-Trautman spacetimes and allows us to measure both the energies and momenta radiated in a gauge-invariant manner. At the same time, this simpler setup provides the qualitative and quantitative features of merging black holes, opening the way to a deeper understanding of the nonlinear dynamics of black-hole spacetimes.
authors.affiliation: Max-Planck-Institut für Gravitationsphysik, Albert Einstein Institut, Potsdam, Germany.
authors.forename: Luciano
authors.initials: L
authors.lastname: Rezzolla
authors.forename: Rodrigo P
authors.initials: RP
authors.lastname: Macedo
authors.forename: José Luis
authors.initials: JL
authors.lastname: Jaramillo