**Publication date:** Oct 1998

**Abstract:**

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.

**Authors:**

Stuchlik, Z.;