400 research outputs found
A Slowly Rotating Charged Black Hole in Five Dimensions
Black hole solutions in higher dimensional Einstein and Einstein-Maxwell
gravity have been discussed by Tangherlini as well as Myers and Perry a long
time ago. These solutions are the generalizations of the familiar
Schwarzschild, Reissner-Nordstrom and Kerr solutions of four-dimensional
general relativity. However, higher dimensional generalization of the
Kerr-Newman solution in four dimensions has not been found yet. As a first step
in this direction I shall report on a new solution of the Einstein-Maxwell
system of equations that describes an electrically charged and slowly rotating
black hole in five dimensions.Comment: Talk given at GR17: 17th International Conference on General
Relativity and Gravitation, Dublin, 18-24 Jule,2004 ; Corrected typos, minor
changes, new formula adde
Stationary perturbations and infinitesimal rotations of static Einstein-Yang-Mills configurations with bosonic matter
Using the Kaluza-Klein structure of stationary spacetimes, a framework for
analyzing stationary perturbations of static Einstein-Yang-Mills configurations
with bosonic matter fields is presented. It is shown that the perturbations
giving rise to non-vanishing ADM angular momentum are governed by a
self-adjoint system of equations for a set of gauge invariant scalar
amplitudes. The method is illustrated for SU(2) gauge fields, coupled to a
Higgs doublet or a Higgs triplet. It is argued that slowly rotating black holes
arise generically in self-gravitating non-Abelian gauge theories with bosonic
matter, whereas, in general, soliton solutions do not have rotating
counterparts.Comment: 8 pages, revtex, no figure
Gravitational collapse of spherically symmetric plasmas in Einstein-Maxwell spacetimes
We utilize a recent formulation of a spherically symmetric spacetime endowed
with a general decomposition of the energy momentum tensor [Phys. Rev. D, 75,
024031 (2007)] to derive equations governing spherically symmetric
distributions of electromagnetic matter. We show the system reduces to the
Reissner-Nordstrom spacetime in general, spherically symmetric coordinates in
the vacuum limit. Furthermore, we show reduction to the charged Vaidya
spacetime in non-null coordinates when certain equations of states are chosen.
A model of gravitational collapse is discussed whereby a charged fluid resides
within a boundary of finite radial extent on the initial hypersurface, and is
allowed to radiate charged particles. Our formalism allows for the discussion
of all regions in this model without the need for complicated matching schemes
at the interfaces between successive regions. As further examples we consider
the collapse of a thin shell of charged matter onto a Reissner-Nordstrom black
hole. Finally, we reduce the entire system of equations to the static case such
that we have the equations for hydrostatic equilibrium of a charged fluid.Comment: Accepted for publication in Phys. Rev.
Naked Singularity of the Vaidya-deSitter Spacetime and Cosmic Censorship Hypothesis
We investigate the formation of a locally naked singularity in the collapse
of radiation shells in an expanding Vaidya-deSitter background. This is
achieved by considering the behaviour of non-spacelike and radial geodesics
originating at the singularity. A specific condition is determined for the
existence of radially outgoing, null geodesics originating at the singularity
which, when this condition is satisfied, becomes locally naked. This condition
turns out to be the same as that in the collapse of radiation shells in an
asymptotically flat background. Therefore, we have, at least for the case
considered here, established that the asymptotic flatness of the spacetime is
not essential for the development of a locally naked singularity. Our result
then unequivocally supports the view that no special role be given to
asymptotic observers (or, for that matter, any set of observers) in the
formulation of the Cosmic Censorship Hypothesis.Comment: submitted Oct. 1997, Revised Version, to be published Gen. Rel.
Grav., Latex file, 9 page
Singularity in Gravitational Collapse of Plane Symmetric Charged Vaidya Spacetime
We study the final outcome of gravitational collapse resulting from the plane
symmetric charged Vaidya spacetime. Using the field equations, we show that the
weak energy condition is always satisfied by collapsing fluid. It is found that
the singularity formed is naked. The strength of singularity is also
investigated by using Nolan's method. This turns out to be a strong curvature
singularity in Tipler's sense and hence provides a counter example to the
cosmic censorship hypothesis.Comment: 8 pages, accepted for publication in Mod. Phys. Lett
From Gravitons to Gravity: Myths and Reality
There is a general belief, reinforced by statements in standard textbooks,
that: (i) one can obtain the full non-linear Einstein's theory of gravity by
coupling a massless, spin-2 field self-consistently to the total
energy momentum tensor, including its own; (ii) this procedure is unique and
leads to Einstein-Hilbert action and (iii) it only uses standard concepts in
Lorentz invariant field theory and does not involve any geometrical
assumptions. After providing several reasons why such beliefs are suspect --
and critically re-examining several previous attempts -- we provide a detailed
analysis aimed at clarifying the situation. First, we prove that it is
\textit{impossible} to obtain the Einstein-Hilbert (EH) action, starting from
the standard action for gravitons in linear theory and iterating repeatedly.
Second, we use the Taylor series expansion of the action for Einstein's theory,
to identify the tensor , to which the graviton field
couples to the lowest order. We show that the second rank tensor
is {\it not} the conventional energy momentum tensor
of the graviton and provide an explanation for this feature. Third, we
construct the full nonlinear Einstein's theory with the source being spin-0
field, spin-1 field or relativistic particles by explicitly coupling the spin-2
field to this second rank tensor order by order and summing
up the infinite series. Finally, we construct the theory obtained by self
consistently coupling to the conventional energy momentum tensor
order by order and show that this does {\it not} lead to Einstein's
theory. (condensed).Comment: revtex; 19 pages; no figure
Corrections and Comments on the Multipole Moments of Axisymmetric Electrovacuum Spacetimes
Following the method of Hoenselaers and Perj\'{e}s we present a new corrected
and dimensionally consistent set of multipole gravitational and electromagnetic
moments for stationary axisymmetric spacetimes. Furthermore, we use our results
to compute the multipole moments, both gravitational and electromagnetic, of a
Kerr-Newman black hole.Comment: This is a revised and corrected versio
Charged Annular Disks and Reissner-Nordstr\"{o}m Type Black Holes from Extremal Dust
We present the first analytical superposition of a charged black hole with an
annular disk of extremal dust. In order to obtain the solutions, we first solve
the Einstein-Maxwell field equations for sources that represent disk-like
configurations of matter in confomastatic spacetimes by assuming a functional
dependence among the metric function, the electric potential and an auxiliary
function,which is taken as a solution of the Laplace equation. We then employ
the Lord Kelvin Inversion Method applied to models of finite extension in order
to obtain annular disks. The structures obtained extend to infinity, but their
total masses are finite and all the energy conditions are satisfied. Finally,
we observe that the extremal Reissner-Nordstr\"{o}m black hole can be embedded
into the center of the disks by adding a boundary term in the inversion.Comment: 17 revtex pages, 8 eps figure
Kaluza-Klein Multi-Black Holes in Five-Dimensional Einstein-Maxwell Theory
We construct the Kaluza-Klein multi-black hole solutions on the
Gibbons-Hawking multi-instanton space in the five-dimensional Einstein-Maxwell
theory. We study geometric properties of the multi-black hole solutions. In
particular, unlike the Gibbons-Hawking multi-instanton solutions, each
nut-charge is able to take a different value due to the existence of black hole
on it. The spatial cross section of each horizon can be admitted to have the
topology of a different lens space L(n;1)=S^3/Z_n addition to S^3.Comment: 8 pages, to be published in Classical and Quantum Gravit
All electro--vacuum Majumdar--Papapetrou space--times with nonsingular black holes
We show that all Majumdar--Papapetrou electrovacuum space--times with a
non--empty black hole region and with a non--singular domain of outer
communications are the standard Majumdar--Papapetrou space--times.Comment: 9 pages, Late
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