Publication date: Dec 2013
Abstract:
Equatorial circular orbits of test particles in the Kerr-anti-de Sitter
black-hole and naked-singularity spacetimes are analyzed and their
properties like the existence, orientation and stability are discussed.
Due to the attractive cosmological constant (), all particles moving
along equatorial orbits are still bound in the gravitational field of
the central object. In general, there are two families of equatorial
circular orbits. Particles moving along minus-family orbits possess
negative angular momentum and, thus, they are counterrotating from the
point of view of the locally non-rotating frames (LNRF). Particles
moving along plus-family orbits possess, in most cases, positive angular
momentum and belong to corotating particles from the point of view of
the LNRF. Nevertheless, in stationary regions inside black holes and
also near naked singularities with appropriately chosen value of the
cosmological constant and rotational parameter , there are also
counterrotating plus-family circular orbits. Moreover, in spacetimes
with , some of these orbits are characterized by negative specific
energy, indicating the bounding energy of the particle, moving along
such an orbit, higher than its rest energy. In black-hole spacetimes,
all such orbits are radially unstable, but in naked-singularity
spacetimes, stable counterrotating orbits with negative specific energy
exist.
Authors:
Slaný, Petr; Pokorná, Miroslava; Stuchlík, Zdeněk;