Publications

Abstract

Although black holes are eminent manifestations of very strong gravity, the geometry of space-time
around and even inside them can be significantly affected by additional bodies present in their
surroundings. We study such an influence within static and axially symmetric (electro)vacuum spacetimes
described by exact solutions of Einstein’s equations, considering astrophysically motivated
configurations (such as black holes surrounded by rings) as well as those of pure academic interest
(such as specifically “tuned” systems of multiple black holes). The geometry is represented by the simplest
invariants determined by the metric (the lapse function) and its gradient (gravitational acceleration), with
special emphasis given to curvature (the Kretschmann and Ricci-square scalars). These quantities are
analyzed and their level surfaces plotted both above and below the black-hole horizons, in particular near
the central singularities. Estimating that the black hole could be most strongly affected by the other black
hole, we focus, in this first paper, on the Majumdar-Papapetrou solution for a binary black hole and
compare the deformation caused by “the other” hole (and the electrostatic field) with that induced by
rotational dragging in the well-known Kerr and Kerr-Newman solutions.