We study the motion of current carrying charged string loops in the
Reissner-Nordström black hole background combining the gravitational and
electromagnetic field. Introducing new electromagnetic interaction
between central charge and charged string loop makes the string loop
equations of motion to be non-integrable even in the flat spacetime
limit, but it can be governed by an effective potential even in the
black hole background. We classify different types of the string loop
trajectories using effective potential approach, and we compare the
innermost stable string loop positions with loci of the charged particle
innermost stable orbits. We examine string loop small oscillations
around minima of the string loop effective potential, and we plot radial
profiles of the string loop oscillation frequencies for both the radial
and vertical modes. We construct charged string loop quasi-periodic
oscillations model and we compare it with observed data from
microquasars GRO 1655-40, XTE 1550-564, and GRS 1915+105. We also study
the acceleration of current carrying string loops along the vertical
axis and the string loop ejection from RN black hole neighbourhood,
taking also into account the electromagnetic interaction.
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Super-massive black holes (SMBHs) hosted in active galactic nuclei
(AGNs) can be characterized by multi-accreting periods as the attractors
interact with the environment during their life-time. These multi-
accretion episodes should leave traces in the matter orbiting the
attractor. Counterrotating and even misaligned structures orbiting
around the SMBHs would be consequences of these episodes. Our task in
this work is to consider situations where such accretions occur and to
trace their remnants represented by several toroidal accreting fluids,
corotating or counterrotating relative to the central Kerr attractor,
and created in various regimes during the evolution of matter
configurations around SMBHs. We focus particularly on the emergence of
matter instabilities, i.e., tori collisions, accretion onto the central
Kerr black hole, or creation of jet-like structures (proto-jets). Each
orbiting configuration is governed by the general relativistic
hydrodynamic Boyer condition of equilibrium configurations of rotating
perfect fluid. We prove that sequences of configurations and hot points,
where an instability occurs, characterize the Kerr SMBHs, depending
mainly on their spin-mass ratios. The occurrence of tori accretion or
collision are strongly constrained by the fluid rotation with respect to
the central black hole and the relative rotation with respect to each
other. Our investigation provides characteristic of attractors where
traces of multi-accreting episodes can be found and observed.
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The possibility that two toroidal accretion configurations may be
orbiting around a~super--massive Kerr black hole has been addressed.
Such tori may be formed during different stages of the Kerr attractor
accretion history. We consider the relative rotation of the tori and the
corotation or counterrotation of a~single torus with respect to the Kerr
attractor. We give classification of the couples of accreting and non--
accreting tori in dependence on the Kerr black hole dimensionless spin.
We demonstrate that only in few cases a~double accretion tori system may
be formed under specific conditions.
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We study the dynamics of charged test particles in the vicinity of a
black hole immersed into an asymptotically uniform external magnetic
field. A real magnetic field around a black hole will be far away from
to be completely regular and uniform, a uniform magnetic field is used
as linear approximation. Ionized particle acceleration, charged particle
oscillations and synchrotron radiation of moving charged particle have
been studied.
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We investigate particle motion and collisions in the vicinity of
rotating black holes immersed in combined cosmological quintessential
scalar field and external magnetic field. The quintessential dark-energy
field governing the spacetime structure is characterized by the
quintessential state parameter ωq ∈ (-1; -1/3) characterizing its
equation of state, and the quintessential field-intensity parameter c
determining the static radius where the black hole attraction is just
balanced by the quintessential repulsion. The magnetic field is assumed
to be test field that is uniform close to the static radius, where the
spacetime is nearly flat, being characterized by strength B there.
Deformations of the test magnetic field in vicinity of the black hole,
caused by the Ricci non-flat spacetime structure are determined. General
expression of the center-of-mass energy of the colliding charged or
uncharged particles near the black hole is given and discussed in
several special cases. In the case of nonrotating black holes, we
discuss collisions of two particles freely falling from vicinity of the
static radius, or one such a particle colliding with charged particle
revolving at the innermost stable circular orbit. In the case of
rotating black holes, we discuss briefly particles falling in the
equatorial plane and colliding in close vicinity of the black hole
horizon, concentrating attention to the interplay of the effects of the
quintessential field and the external magnetic field. We demonstrate
that the ultra-high center-of-mass energy can be obtained for black
holes placed in an external magnetic field for an infinitesimally small
quintessential field-intensity parameter c; the center-of-mass energy
decreases if the quintessential field-intensity parameter c increases.
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In this work we investigate the motion of free particle in the field of
strongly gravitating object which is embedded into dust cosmological
background. We use newly obtained exact solution of Einstein equations
in comoving coordinates for the system under consideration in case of
zero spatial curvature. Observable velocity of the particle moving
relatively to the observer comoving with cosmological expansion is found
from geodesic equations.
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We introduce a general transformation leading to an integral form of
pressure equations characterizing equilibrium configurations of charged
perfect fluid circling in strong gravitational and combined
electromagnetic fields. The transformation generalizes our recent
analytical treatment applicable to electric or magnetic fields treated
separately along with the gravitational one. As an example, we present a
particular solution for a fluid circling close to a charged rotating
black hole immersed in an asymptotically uniform magnetic field.
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The possibility that two toroidal accretion configurations may be
orbiting around a super-massive Kerr black hole has been addressed. Such
tori may be formed during different stages of the Kerr attractor
accretion history. We consider the relative rotation of the tori and the
corotation or counterrotation of a single torus with respect to the Kerr
attractor. We give classification of the couples of accreting and non-
accreting tori in dependence on the Kerr black hole dimensionless spin.
We demonstrate that only in few cases a double accretion tori system may
be formed under specific conditions.
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We demonstrate that the generic charged rotating regular black hole
solutions of general relativity coupled to non-linear electrodynamics,
obtained by using the alternate Newman-Janis algorithm, introduces only
small (on level 10-2) inconsistency in the behaviour of the
electrodynamics Lagrangian. This approves application of these analytic
and simple solutions as astrophysically relevant, sufficiently precise
approximate solutions describing rotating regular black holes.
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In this work we present investigation of the escape cones of null-
geodesics from the interior of rotating homogeneous compact stars in the
model, where only terms linear in the star's rotational frequency are
assumed. We focus on the single model of the star with particular radius
R = 2.8M (using units in which c = G = 1) rotating with different values
of angular momentum J. We vary the position of the isotropically
radiating source both in radial and latitudinal direction and we show
the impact of the position and the rotational rate on the shape of the
escape cone of null-geodesics. We find that even for small rotational
rate corresponding to j = J/M2 = 0.1 the impact on the escape cones is
rather strong. The escape cones are no longer symmetrical around radial
direction, and it is clearly seen that the radiation in the direction of
the rotation can easily reach the infinity. On the other hand, the
radiation in the direction opposite to the rotation will be trapped in
the interior of the star. We discuss possible astrophysical relevance of
our results.
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