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    Charged string loops in Reissner-Nordström black hole background

    by Zdeněk Stuchlík· Březen 01, 2018· in Fyzika· 0 comments
    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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    Tori sequences as remnants of multiple accreting periods of Kerr SMBHs

    by Zdeněk Stuchlík· Březen 01, 2018· in Fyzika· 0 comments
    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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    Constraints on two accretion disks centered on the equatorial plane of a Kerr SMBH

    by Zdeněk Stuchlík· Leden 01, 2018· in Fyzika· 0 comments
    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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    Some astrophysical processes around magnetized black hole

    by Zdeněk Stuchlík· Leden 01, 2018· in Fyzika· 0 comments
    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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    Effect of an external magnetic field on particle acceleration by a rotating black hole surrounded with quintessential energy

    by Zdeněk Stuchlík· Leden 01, 2018· in Fyzika· 0 comments
    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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    The motion of the test particle near the black hole embedded into dust: The flat space case

    by Zdeněk Stuchlík· Prosinec 01, 2017· in Fyzika· 0 comments
    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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    Analytical solution for charged fluid pressure profiles – circulation in combined electromagnetic field

    by Zdeněk Stuchlík· Prosinec 01, 2017· in Fyzika· 0 comments
    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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    Constraints on two accretion disks centered on the equatorial plane of a Kerr SMBH

    by Zdeněk Stuchlík· Prosinec 01, 2017· in Fyzika· 0 comments
    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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    Note on the character of the generic rotating charged regular black holes in general relativity coupled to nonlinear electrodynamics

    by Zdeněk Stuchlík· Prosinec 01, 2017· in Fyzika· 0 comments
    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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    Escape cones of null-geodesics from the interior of rotating compact stars

    by Zdeněk Stuchlík· Prosinec 01, 2017· in Fyzika· 0 comments
    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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