368 research outputs found
Energy flux through the horizon in the black hole-domain wall systems
We study various configurations in which a domain wall (or cosmic string),
described by the Nambu-Goto action, is embedded in a background space-time of a
black hole in and higher dimensional models. We calculate energy fluxes
through the black hole horizon. In the simplest case, when a static domain wall
enters the horizon of a static black hole perperdicularly, the energy flux is
zero. In more complicated situations, where parameters which describe the
domain wall surface are time and position dependent, the flux is non-vanishing
is principle. These results are of importance in various conventional
cosmological models which accommodate the existence of domain walls and strings
and also in brane world scenarios.Comment: references added, accepted for publication in JHE
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
Thorny Spheres and Black Holes with Strings
We consider thorny spheres, that is 2-dimensional compact surfaces which are
everywhere locally isometric to a round sphere except for a finite number
of isolated points where they have conical singularities. We use thorny spheres
to generate, from a spherically symmetric solution of the Einstein equations,
new solutions which describe spacetimes pierced by an arbitrary number of
infinitely thin cosmic strings radially directed. Each string produces an angle
deficit proportional to its tension, while the metric outside the strings is a
locally spherically symmetric solution. We prove that there can be arbitrary
configurations of strings provided that the directions of the strings obey a
certain equilibrium condition. In general this equilibrium condition can be
written as a force-balance equation for string forces defined in a flat 3-space
in which the thorny sphere is isometrically embedded, or as a constraint on the
product of holonomies around strings in an alternative 3-space that is flat
except for the strings. In the case of small string tensions, the constraint
equation has the form of a linear relation between unit vectors directed along
the string axes.Comment: 37 pages, 11 figure
Soap Bubbles in Outer Space: Interaction of a Domain Wall with a Black Hole
We discuss the generalized Plateau problem in the 3+1 dimensional
Schwarzschild background. This represents the physical situation, which could
for instance have appeared in the early universe, where a cosmic membrane (thin
domain wall) is located near a black hole. Considering stationary axially
symmetric membranes, three different membrane-topologies are possible depending
on the boundary conditions at infinity: 2+1 Minkowski topology, 2+1 wormhole
topology and 2+1 black hole topology.
Interestingly, we find that the different membrane-topologies are connected
via phase transitions of the form first discussed by Choptuik in investigations
of scalar field collapse. More precisely, we find a first order phase
transition (finite mass gap) between wormhole topology and black hole topology;
the intermediate membrane being an unstable wormhole collapsing to a black
hole. Moreover, we find a second order phase transition (no mass gap) between
Minkowski topology and black hole topology; the intermediate membrane being a
naked singularity.
For the membranes of black hole topology, we find a mass scaling relation
analogous to that originally found by Choptuik. However, in our case the
parameter is replaced by a 2-vector parametrizing the solutions.
We find that where . We also find a periodic wiggle in the scaling relation.
Our results show that black hole formation as a critical phenomenon is far
more general than expected.Comment: 15 pages, Latex, 4 figures include
STATIONARY STRINGS AND 2-D BLACK HOLES
A general description of string excitations in stationary spacetimes is
developed. If a stationary string passes through the ergosphere of a
4-dimensional black hole, its world-sheet describes a 2-dimensional black (or
white) hole with horizon coinciding with the static limit of the 4-dimensional
black hole. Mathematical results for 2-dimensional black holes can therefore be
applied to physical objects (say) cosmic strings in the vicinity of Kerr black
holes. An immediate general result is that the string modes are thermally
excited. The string excitations are determined by a coupled system of scalar
field equations in the world-sheet metric. In the special case of excitations
propagating along a stationary string in the equatorial plane of the
Kerr-Newman black hole, they reduce to the -wave scalar field equations in
the 4-dimensional Reissner-Nordstr\"{o}m black hole. We briefly discuss
possible applications of our results to the black hole information puzzle.Comment: 13 pages, Late
Quasinormal mode characterization of evaporating mini black holes
According to recent theoretical developments, it might be possible to produce
mini black holes in the high energy experiments in the LHC at CERN. We propose
here a model based on the -dimensional Vaidya metric in double null
coordinates for these decaying black holes. The associated quasinormal modes
are considered. It is shown that only in the very last instants of the
evaporation process the stationary regime for the quasinormal modes is broken,
implying specific power spectra for the perturbations around these mini
black-holes. From scattered fields one could recover, in principle, the black
hole parameters as well as the number of extra dimensions. The still mysterious
final fate of such objects should not alter significantly our main conclusions.Comment: v4: 9 pages, 3 figures. Minor correction
Interaction of a brane with a moving bulk black hole
We study the interaction of an n-dimensional topological defect (n-brane)
described by the Nambu-Goto action with a higher-dimensional Schwarzschild
black hole moving in the bulk spacetime. We derive the general form of the
perturbation equations for an n-brane in the weak field approximation and solve
them analytically in the most interesting cases. We specially analyze
applications to brane world models. We calculate the induced geometry on the
brane generated by a moving black hole. From the point of view of a brane
observer, this geometry can be obtained by solving (n+1)-dimensional Einstein's
equations with a non-vanishing right hand side. We calculate the effective
stress-energy tensor corresponding to this `shadow-matter'. We explicitly show
that there exist regions on the brane where a brane observer sees an apparent
violation of energy conditions. We also study the deflection of light
propagating in the region of influence of this `shadow matter'.Comment: version accepted for publication in Phys. Rev.
Quantum backreaction of massive fields and self-consistent semiclassical extreme black holes and acceleration horizons
We consider the effect of backreaction of quantized massive fields on the
metric of extreme black holes (EBH). We find the analytical approximate
expression for the stress-energy tensor for a scalar (with an arbitrary
coupling), spinor and vector fields near an event horizon. We show that,
independent of a concrete type of EBH, the energy measured by a freely falling
observer is finite on the horizon, so that quantum backreaction is consistent
with the existence of EBH. For the Reissner-Nordstrom EBH with a total mass
M_{tot} and charge Q we show that for all cases of physical interest M_{tot}<
Q. We also discuss different types of quantum-corrected Bertotti-Robinson
spacetimes, find for them exact self-consistent solutions and consider
situations in which tiny quantum corrections lead to the qualitative change of
the classical geometry and topology. In all cases one should start not from a
classical background with further adding quantum corrections but from the
quantum-corrected self-consistent geometries from the very beginning.Comment: Minor corrections. To appear in Phys. Rev.
Stationary strings and branes in the higher-dimensional Kerr-NUT-(A)dS spacetimes
We demonstrate complete integrability of the Nambu-Goto equations for a
stationary string in the general Kerr-NUT-(A)dS spacetime describing the
higher-dimensional rotating black hole. The stationary string in D dimensions
is generated by a 1-parameter family of Killing trajectories and the problem of
finding a string configuration reduces to a problem of finding a geodesic line
in an effective (D-1)-dimensional space. Resulting integrability of this
geodesic problem is connected with the existence of hidden symmetries which are
inherited from the black hole background. In a spacetime with p mutually
commuting Killing vectors it is possible to introduce a concept of a
-brane, that is a p-brane with the worldvolume generated by these fields
and a 1-dimensional curve. We discuss integrability of such -branes in the
Kerr-NUT-(A)dS spacetime.Comment: 8 pages, no figure
Propagation of perturbations along strings
A covariant formalism for physical perturbations propagating along a string
in an arbitrary curved spacetime is developed. In the case of a stationary
string in a static background the propagation of the perturbations is described
by a wave-equation with a potential consisting of 2 terms: The first term
describing the time-dilation and the second is connected with the curvature of
space. As applications of the developed approach the propagation of
perturbations along a stationary string in Rindler, de Sitter, Schwarzschild
and Reissner-Nordstrom spacetimes are investigated.Comment: 18 pages, LaTeX, Nordita-93/17
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