3,676 research outputs found
Stationary strings near a higher-dimensional rotating black hole
We study stationary string configurations in a space-time of a
higher-dimensional rotating black hole. We demonstrate that the Nambu-Goto
equations for a stationary string in the 5D Myers-Perry metric allow a
separation of variables. We present these equations in the first-order form and
study their properties. We prove that the only stationary string configuration
which crosses the infinite red-shift surface and remains regular there is a
principal Killing string. A worldsheet of such a string is generated by a
principal null geodesic and a timelike at infinity Killing vector field. We
obtain principal Killing string solutions in the Myers-Perry metrics with an
arbitrary number of dimensions. It is shown that due to the interaction of a
string with a rotating black hole there is an angular momentum transfer from
the black hole to the string. We calculate the rate of this transfer in a
spacetime with an arbitrary number of dimensions. This effect slows down the
rotation of the black hole. We discuss possible final stationary configurations
of a rotating black hole interacting with a string.Comment: 13 pages, contains additianal material at the end of Section 8, also
small misprints are correcte
Scattering of Straight Cosmic Strings by Black Holes: Weak Field Approximation
The scattering of a straight, infinitely long string moving with velocity
by a black hole is considered. We analyze the weak-field case, where the impact
parameter () is large, and obtain exact solutions to the equations of
motion. As a result of scattering, the string is displaced in the direction
perpendicular to the velocity by an amount , where . The second
term dominates at low velocities . The late-time
solution is represented by a kink and anti-kink, propagating in opposite
directions at the speed of light, and leaving behind them the string in a new
``phase''. The solutions are applied to the problem of string capture, and are
compared to numerical results.Comment: 19 pages, 5 figure
Statistical Mechanics of Charged Black Holes in Induced Einstein-Maxwell Gravity
The statistical origin of the entropy of charged black holes in models of
induced Einstein-Maxwell gravity is investigated. The constituents inducing the
Einstein-Maxwell action are charged and interact with an external gauge
potential. This new feature, however, does not change divergences of the
statistical-mechanical entropy of the constituents near the horizon. It is
demonstrated that the mechanism of generation of the Bekenstein-Hawking entropy
in induced gravity is universal and it is basically the same for charged and
neutral black holes. The concrete computations are carried out for induced
Einstein-Maxwell gravity with a negative cosmological constant in three
space-time dimensions.Comment: 16 pages, latex, no figure
Rotating non-asymptotically flat black rings in charged dilaton gravity
We derive new rotating, non-asymptotically flat black ring solutions in
five-dimensional Einstein-Maxwell-dilaton gravity with dilaton coupling
constant which arises from a six-dimensional Kaluza-Klein
theory. As a limiting case we also find new rotating, non-asymptotically flat
five-dimensional black holes. The solutions are analyzed and the mass, angular
momentum and charge are computed. A Smarr-like relation is found. It is shown
that the first law of black hole thermodynamics is satisfied.Comment: 21 pages, LaTeX; v2 a reference added, typos correcte
Proton spin polarizabilities from polarized Compton scattering
Polarized Compton scattering off the proton is studied within the framework
of subtracted dispersion relations for photon energies up to 300 MeV. As a
guideline for forthcoming experiments, we focus the attention on the role of
the proton's spin polarizabilities and investigate the most favorable
conditions to extract them with a minimum of model dependence. We conclude that
a complete separation of the four spin polarizabilities is possible, at photon
energies between threshold and the region, provided one can
achieve polarization measurements with an accuracy of a few percent.Comment: 26 pages, 7 figures
Thermonuclear burn-up in deuterated methane
The thermonuclear burn-up of highly compressed deuterated methane CD is
considered in the spherical geometry. The minimal required values of the
burn-up parameter are determined for various
temperatures and densities . It is shown that thermonuclear burn-up
in becomes possible in practice if its initial density exceeds
. Burn-up in CDT methane
requires significantly ( 100 times) lower compressions. The developed
approach can be used in order to compute the critical burn-up parameters in an
arbitrary deuterium containing fuel
Thermodynamics and Statistical Mechanics of Induced Liouville Gravity
In this paper we describe a Liouville gravity which is induced by a set of
quantum fields (constituents) and represents a two-dimensional analog of
Sakharov's induced gravity. The important feature of the considered theory is
the presence of massless constituents which are responsible for the appearance
of the induced Liouville field. The role of the massive constituents is only to
induce the cosmological constant. We consider the instanton solutions of the
Euclidean Liouville gravity with negative and zero cosmological constants, some
instantons being interpreted as two-dimensional anti-de Sitter black
holes. We study thermodynamics of all the solutions and conclude that their
entropy is completely determined by the statistical-mechanical entropy of the
massless constituents. This shows, in particular, that the constituents of the
induced gravity are the true degrees of freedom of black holes. Special
attention is also paid to the induced Liouville gravity with zero cosmological
constant on a torus. We demonstrate the equivalence of its thermodynamics to
the thermodynamics of BTZ black holes and comment on computations of the BTZ
black hole entropy.Comment: 22 pages, latex, no figure
Accretion of non-minimally coupled generalized Chaplygin gas into black holes
The mass evolution of Schwarzschild black holes by the absorption of scalar
fields is investigated in the scenario of the generalized Chaplygin gas (GCG).
The GCG works as a unification picture of dark matter plus dark energy that
naturally accelerates the expansion of the Universe. Through elements of the
quasi-stationary approach, we consider the mass evolution of Schwarzschild
black holes accreted by non-minimally coupled cosmological scalar fields
reproducing the dynamics of the GCG. As a scalar field non-minimally coupled to
the metrics, such an exotic content has been interconnected with accreting
black holes. The black hole increasing masses by the absorption of the gas
reflects some consistence of the accretion mechanism with the hypothesis of the
primordial origin of supermassive black holes. Our results effectively show
that the non-minimal coupling with the GCG dark sector accelerates the
increasing of black hole masses. Meanwhile some exotic features can also be
depicted for specific ranges of the non-minimal coupling in which the GCG
dynamics is substantially modified.Comment: 13 pages, 03 figure
Interaction of higher-dimensional rotating black holes with branes
We study interaction of rotating higher dimensional black holes with a brane
in space-times with large extra dimensions. We demonstrate that in a general
case a rotating black hole attached to a brane can loose bulk components of its
angular momenta. A stationary black hole can have only those components of the
angular momenta which are connected with Killing vectors generating
transformations preserving a position of the brane. In a final stationary state
the null Killing vector generating the black hole horizon is tangent to the
brane. We discuss first the interaction of a cosmic string and a domain wall
with the 4D Kerr black hole. We then prove the general result for slowly
rotating higher dimensional black holes interacting with branes. The
characteristic time when a rotating black hole with the gravitational radius
reaches this final stationary state is , where
is the higher dimensional gravitational coupling constant, is the
brane tension, and is the number of extra dimensions.Comment: Version published in Class. Quant. Gra
Quantum Radiation of a Uniformly Accelerated Refractive Body
We study quantum radiation generated by an accelerated motion of a small body
with a refractive index n which differes slightly from 1. To simplify
calculations we consider a model with a scalar massless field. We use the
perturbation expansion in a small parameter n-1 to obtain a correction to the
vacuum Hadamard function for a uniformly accelerated motion of the body. We
obtain the vacuum expectation for the energy density flux in the wave zone and
discuss its properties.Comment: 16 pages, 1 figur
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