Tidal dynamics of black holes and self-force in strong gravitational fields

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The proposal is divided into two broad streams, the tidal dynamics of black holes, and the self-force in spacetimes with matter. Binary systems of black holes are among the most promising and exciting sources of gravitational waves, and the tidal forces exerted on one black hole by its companion can have a strong impact on the dynamics of the binary system when its orbit is very tight, close to merger. For example, the tidal forces can torque the black hole and produce a change of spin, and they can heat the black hole and produce a change of mass; these processes affect the orbital motion and the form of the gravitational waves emitted by the system. These signatures can be measured and used to test the detailed predictions of general relativity concerning black holes. In the next granting cycle I will work toward obtaining a much better understanding of this tidal dynamics, focusing mostly on the astrophysically realistic case of rotating black holes. The self-force refers to a deviation from geodesic motion that occurs when a particle moving in spacetime can no longer be considered to be a test body. This happens, for example, when the particle carries an electric charge; in this case the charge produces an electromagnetic field that interacts with the ambiant spacetime curvature, and the field gives rise to a net force acting on the particle. This also happens when the particle's mass is sufficiently large that it affects the structure of spacetime around it; the gravitational perturbation creates an effective force that prevents the particle from moving on a geodesic of the background spacetime. In the next granting cycle I will continue my work on the electromagnetic and gravitational self-force. In particular, I will determine whether the self-force can act as a cosmic censor, preventing a black hole from being destroyed by absorbing a charged particle that would drive its charge beyond the allowed limit.