We investigate possible signatures of a Kerr naked singularity (superspinar) in the profiled spectral lines of radiation emitted by monochromatically and isotropically radiating point sources forming a Keplerian ring or disc around such compact object. We have found out that the profiled spectral line of the radiating Keplerian ring can be splitted into two parts due to the fact that there is no event horizon in the naked singularity spacetimes.
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Kerr naked singularities (superspinars) have to be efficiently converted to a black hole due to accretion from Keplerian discs. In the final stages of the conversion process the near-extreme Kerr naked singularities (superspinars) provide a variety of extraordinary physical phenomena. Such superspinning Kerr geometries can serve as an efficient accelerator for extremely high-energy collisions enabling direct and clear demonstration of the outcomes of the collision processes. We shall discuss the efficiency and visibility of the ultra-high energy collisions in the deepest parts of the gravitational well of superspinning near-extreme Kerr geometries for the whole variety of particles freely falling from infinity. We demonstrate that the ultra high-energy processes can be obtained with no fine tuning of the motion constants and the products of the collision can escape to infinity with efficiency higher than in the case of the near-extreme black holes.
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We study acceleration of current-carrying string loops governed by presence of an outer tension barrier and an inner angular momentum barrier in the field of black holes. Relativistic current carrying strings moving axisymmetrically along the axis of a black hole could in a simplified way represent plasma that exhibits associated string-like behavior. We demonstrate that string loops can be scattered near the black hole horizon and the energy of string oscillations can be efficiently converted to the energy of their linear motion. Such a transmutation effect can potentially represent acceleration of jets in active galactic nuclei and microquasars.
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Using the pseudo-Newtonian (PN) potential, we estimate the influence of
the repulsive cosmological constant Ʌ ~ 1.3×10-56
cm-2 implied by recent cosmological tests onto the motion of
both Small and Large Magellanic Clouds (SMC and LMC) in the
gravitational field of the Milky Way. The role of the cosmological
constant is most conspicuous when binding mass is estimated for the
satellite galaxies. We have found a strong influence of cosmic repulsion
on the total binding mass for both galaxies. We have found that in some
cases, the effect of the cosmic repulsion can be even comparable to the
effects of the dynamical friction and the Andromeda galaxy.
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We investigate possible signatures of a Kerr naked singularity
(superspinar) in the profiled spectral lines of radiation emitted by
monochromatically and isotropically radiating point sources forming a
Keplerian ring or disc around such compact object. We have found out
that the profiled spectral line of the radiating Keplerian ring can be
splitted into two parts due to the fact that there is no event horizon
in the naked singularity spacetimes.
Read More
Kerr naked singularities (superspinars) have to be efficiently converted
to a black hole due to accretion from Keplerian discs. In the final
stages of the conversion process the near-extreme Kerr naked
singularities (superspinars) provide a variety of extraordinary physical
phenomena. Such superspinning Kerr geometries can serve as an efficient
accelerator for extremely high-energy collisions enabling direct and
clear demonstration of the outcomes of the collision processes. We shall
discuss the efficiency and visibility of the ultra-high energy
collisions in the deepest parts of the gravitational well of
superspinning near-extreme Kerr geometries for the whole variety of
particles freely falling from infinity. We demonstrate that the ultra
high-energy processes can be obtained with no fine tuning of the motion
constants and the products of the collision can escape to infinity with
efficiency higher than in the case of the near-extreme black holes.
Read More
We study acceleration of current-carrying string loops governed by
presence of an outer tension barrier and an inner angular momentum
barrier in the field of black holes. Relativistic current carrying
strings moving axisymmetrically along the axis of a black hole could in
a simplified way represent plasma that exhibits associated string-like
behavior. We demonstrate that string loops can be scattered near the
black hole horizon and the energy of string oscillations can be
efficiently converted to the energy of their linear motion. Such a
transmutation effect can potentially represent acceleration of jets in
active galactic nuclei and microquasars.
Read More
We have previously applied several models of high-frequency quasi-periodic oscillations (HF QPOs) to estimate the spin of the central Kerr black hole in the three Galactic microquasars, GRS 1915+105, GRO J1655-40, and XTE J1550-564. Here we explore the alternative possibility that the central compact body is a super-spinning object (or a naked singularity) with the external space-time described by Kerr geometry with a dimensionless spin parameter a ≡ cJ/GM2> 1. We calculate the relevant spin intervals for a subset of HF QPO models considered in the previous study. Our analysis indicates that for all but one of the considered models there exists at least one interval of a> 1 that is compatible with constraints given by the ranges of the central compact object mass independently estimated for the three sources. For most of the models, the inferred values of a are several times higher than the extreme Kerr black hole value a = 1. These values may be too high since the spin of superspinars is often assumed to rapidly decrease due to accretion when a ≫ 1. In this context, we conclude that only the epicyclic and the Keplerian resonance model provides estimates that are compatible with the expectation of just a small deviation from a = 1.
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We study properties of the magnetized toroidal structures orbiting the Kerr superspinars predicted by the string theory. We demonstrate specific features of the unmagnetized perfect fluid tori created in the deep potential well near the surface of the superspinars, enabling clear distinction between Kerr superspinars and black holes. Then we consider the effect of the magnetization of the perfect fluid tori and shift of their properties induced by the presence of the magnetic field.
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We consider equatorial motion of test particles around a rotating Kerr naked singularity in the Randall-Sundrum braneworld scenario and its implications for the properties of Keplerian accretion disks. We demonstrate existence of some unexpected phenomena related to properties of spacetimes having positive braneworld tidal charges. This new phenomenon can be an interesting explanation for extremely high energy cosmic radiation.
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