Comment on “Boosted Kerr black holes in general relativity”

Abstract

We discuss a recently presented boosted Kerr black hole solution which had already been used by other authors. This boosted metric is based on wrong assumptions regarding asymptotic inertial observers and moreover the performed boost is not a proper Lorentz transformation. This note aims to clarify some of the issues when boosting black holes and the necessary care in order to interpret them. As it is wrongly claimed that the presented boosted Kerr metric is of Bondi-Sachs type, we recall out some of the necessary requirements and difficulties, when the casting the Kerr metric into a metric with a surface forming null coordinate.

Magnetized black holes: the role of rotation, boost, and accretion in twisting the field lines and accelerating particles

“…Refer to enlightening discussions by various authors 6,7 and see also the relevant context of these solutions. 8 In the above-mentioned previous papers, we numerically studied escaping orbits and we assessed in detail the role of a broad variety of parameters of the model. Nevertheless, the assumption that initially neutral matter co-rotates with the central black hole, was adopted in all previous analyses.…”