Publication date: Oct 1998
Black holes in spacetimes with a negative vacuum energy, i.e., with an
attractive cosmological constant Λ < 0, are described by the
Kerr-Newman-anti-de Sitter geometry. It is proposed that if the specific
angular momentum of a black hole and the attractive cosmological
constant are combined appropriately, the spacetime can be considered as
consisting of causally disconnected regions with opposite signature of
the metric tensor, corresponding to opposite character of the geometry
outside the black-hole horizons and between the horizons, respectively.
No photons and test particles can cross a surface of degeneracy at a
constant latitudinal coordinate, which separates the causally
disconnected regions. Differences of the properties of the motion of
test particles in the separated regions are discussed. They are given by
the different normalization condition of the equations of motion, i.e.,
motion in the region with the opposite signature is of "tachyonic"
nature. It is demonstrated in the simplest case of uncharged particles
moving along the axis of symmetry.