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General Relativity and Quantum Cosmology, gr-qc, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE,High Energy Physics - Theory, hep-th
Abstract:
The Minkowski background intrinsic to the Kerr-Schild version of the Kerr
metric provides a definition of a boosted spinning black hole. There are two
Kerr-Schild versions corresponding to ingoing or outgoing principal null
directions. The two corresponding Minkowski backgrounds and their associated
boosts differ drastically. This has an important implication for the
gravitational memory effect. A prior analysis of the ejection of a non-spinning
Schwarzschild black hole showed that the memory effect in the nonlinear regime
agrees with the linearized result based upon the retarded Green function only
if the ejection velocity corresponds to a boost symmetry of the ingoing
Minkowski background. A boost with respect to the outgoing Minkowski background
is inconsistent with the absence of ingoing radiation from past null infinity.
We show that this results extends to the ejection of a Kerr black hole and
apply it to set upper and lower bounds for the memory effect resulting from the
collision of two spinning black holes.
