Due to the present indications of the existence of a non-zero cosmological constant, some aspects of the influence of a Lambda not equal to zero on the character of test-particle motion in black-hole backgrounds are discussed. Equations of motion of electrically charged particles and magnetic monopoles are written in the most general Kerr-Newman-de Sitter dyon background. For the Kerr-de Sitter spacetime, the latitudinal motion is examined in detail by using the 'Chinese boxes' technique. The radial motion in the Schwarzschild-de Sitter background is considered with attention devoted to the existence and stability of circular orbits and to the properties of purely radial trajectories. Finally, the possibility of constructing an Einstein-Strauss-de Sitter model of the Universe (i.e. a model of Schwarzschild-de Sitter condensations in the Friedman Universe with a non-zero Lambda-term) is discussed.
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Due to the present indications of the existence of a non-zero
cosmological constant, some aspects of the influence of a Lambda not
equal to zero on the character of test-particle motion in black-hole
backgrounds are discussed. Equations of motion of electrically charged
particles and magnetic monopoles are written in the most general
Kerr-Newman-de Sitter dyon background. For the Kerr-de Sitter spacetime,
the latitudinal motion is examined in detail by using the 'Chinese
boxes' technique. The radial motion in the Schwarzschild-de Sitter
background is considered with attention devoted to the existence and
stability of circular orbits and to the properties of purely radial
trajectories. Finally, the possibility of constructing an
Einstein-Strauss-de Sitter model of the Universe (i.e. a model of
Schwarzschild-de Sitter condensations in the Friedman Universe with a
non-zero Lambda-term) is discussed.
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The latitudinal motion of an electrically charged particle in a dyon
space-time described by the Kerr-Newman metric with both electric and
magnetic charges is investigated. Due to duality invariance this
description holds also for the motion of a magnetic monopole in a field
of a dyon with appropriately chosen charges. The results are compared
with a previous analysis of the test particle motion in the Kerr-Newman
space-time.
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The latitudinal motion of an electrically charged particle in a dyon space-time described by the Kerr-Newman metric with both electric and magnetic charges is investigated. Due to duality invariance this description holds also for the motion of a magnetic monopole in a field of a dyon with appropriately chosen charges. The results are compared with a previous analysis of the test particle motion in the Kerr-Newman space-time.
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The photon trajectories in the Kerr-Newman metric are described in both
the black hole and naked singularity cases. The radial motions of
photons are discussed, and by finding the turning points of the radial
motion, the regions allowed for this motion are determined. The region
of negative radii is considered, and it is found that the qualitative
differences between the Kerr-Newman metric and the Kerr metric occur
only below the inner horizon and around naked singularities. In some
cases stable circular orbits exist in the equatorial plane, and in other
cases there are no spherical orbits on positive radii at all.
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Consideration is given to the evolution of stationary axisymmetric
rotating Kerr naked singularities due to the accretion of matter from
thin corotating disks. Within the framework of the Page-Thorne model of
accretion disks, it is shown that the naked singularity must evolve
towards an extreme black hole state provided sufficient mass is
accreted. Analytical expressions for the time evolution of the Kerr
naked singularity as a function of initial mass and angular momentum are
then obtained for the cases of a constant accretion rate, an accretion
rate proportional to black hole mass, and an accretion rate
self-regulated at the critical rate. It is pointed out that for
accretion in binary systems, singularities of mass less than 10 solar
masses may be converted into black holes only for angular momentum very
close to unity. Effects of the capture of the radiation emitted by the
disk by the singularity or the disk itself and of changes in disk
geometry at the later stages of black hole conversion are also
considered
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