**Publication date:** Mar 2008

**Abstract:**

Properties of the Reissner-Nordstr“om black-hole and naked-singularity

spacetimes with a nonzero cosmological constant are represented by their

geodetical structure and embedding diagrams of the central planes of

both the ordinary geometry and associated optical reference geometry.

Motion of test particles and photons is described in terms of an

appropriate `effective potential.‘ Circular geodesics are discussed and

photon escape cones are determined. In all asymptotically anti-dS black-

hole spacetimes and some asymptotically dS black-hole spacetimes a

region containing stable circular geodesics exists, which allows

accretion processes in the disk regime. The inner region is limited from

below by particles with zero angular momentum that are located in stable

equilibrium positions. The inertial and gravitational forces related to

the optical reference geometry are introduced and specified for the

circular motion. It is shown how the properties of the centrifugal force

are closely related to the properties of the optical reference geometry

embedding diagrams.

**Authors:**

Stuchlík, Zdeněk; Hledík, Stanislav;