1,738 research outputs found
Initial data for gravity coupled to scalar, electromagnetic and Yang-Mills fields
We give ansatze for solving classically the initial value constraints of
general relativity minimally coupled to a scalar field, electromagnetism or
Yang-Mills theory. The results include both time-symmetric and asymmetric data.
The time-asymmetric examples are used to test Penrose's cosmic censorship
inequality. We find that the inequality can be violated if only the weak energy
condition holds.Comment: 16 pages, RevTeX, references added, presentational changes, version
to appear in Phys Rev.
Black Hole Solutions of Kaluza-Klein Supergravity Theories and String Theory
We find U(1)_{E} \times U(1)_{M} non-extremal black hole solutions of
6-dimensional Kaluza-Klein supergravity theories. Extremal solutions were found
by Cveti\v{c} and Youm\cite{C-Y}. Multi black hole solutions are also
presented. After electro-magnetic duality transformation is performed, these
multi black hole solutions are mapped into the the exact solutions found by
Horowitz and Tseytlin\cite{H-T} in 5-dimensional string theory compactified
into 4-dimensions. The massless fields of this theory can be embedded into the
heterotic string theory compactified on a 6-torus. Rotating black hole
solutions can be read off those of the heterotic string theory found by
Sen\cite{Sen3}.Comment: 23 pages text(latex), a figure upon reques
Classical and quantum evolution of non-isentropic hot singular layers in finite-temperature general relativity
The spherically symmetric layer of matter is considered within the frameworks
of general relativity. We perform generalization of the already known theory
for the case of nonconstant surface entropy and finite temperature. We also
propose the minisuperspace model to determine the behaviour of temperature
field and perform the Wheeler-DeWitt quantization.Comment: final version, published in GRG as a lette
A modification of the Chen-Nester quasilocal expressions
Chen and Nester proposed four boundary expressions for the quasilocal
quantities using the covariant Hamiltonian formalism. Based on these four
expressions, there is a simple generalization that one can consider, so that a
two parameter set of boundary expressions can be constructed. Using these
modified expressions, a nice result for gravitational energy-momentum can be
obtained in holonomic frames.Comment: 11 page
Interior of Distorted Black Holes
We study the interior of distorted static axisymmetric black holes. We obtain
a general interior solution and study its asymptotics both near the horizon and
singularity. As a special example, we apply the obtained results to the case of
the so-called `caged' black holes.Comment: 12 pages, 16 figure
Population bound effects on bosonic correlations in non-inertial frames
We analyse the effect of bounding the occupation number of bosonic field
modes on the correlations among all the different spatial-temporal regions in a
setting in which we have a space-time with a horizon along with an inertial
observer. We show that the entanglement between A (inertial observer) and R
(uniformly accelerated observer) depends on the bound N, contrary to the
fermionic case. Whether or not decoherence increases with N depends on the
value of the acceleration a. Concerning the bipartition A-antiR (Alice with an
observer in Rindler's region IV), we show that no entanglement is created
whatever the value of N and a. Furthermore, AR entanglement is very quickly
lost for finite N and for infinite N. We will study in detail the mutual
information conservation law found for bosons and fermions. By means of the
boundary effects associated to N finiteness, we will show that for bosons this
law stems from classical correlations while for fermions it has a quantum
origin. Finally, we will present the strong N dependence of the entanglement in
R-antiR bipartition and compare the fermionic cases with their finite N bosonic
analogs. We will also show the anti-intuitive dependence of this entanglement
on statistics since more entanglement is created for bosons than for their
fermion counterparts.Comment: revtex 4, 12 pages, 10 figures. Added Journal ref
A new perspective on Gravity and the dynamics of Spacetime
The Einstein-Hilbert action has a bulk term and a surface term (which arises
from integrating a four divergence). I show that one can obtain Einstein's
equations from the surface term alone. This leads to: (i) a novel, completely
self contained, perspective on gravity and (ii) a concrete mathematical
framework in which the description of spacetime dynamics by Einstein's
equations is similar to the description of a continuum solid in the
thermodynamic limit.Comment: Based on the Essay selected for Honorable Mention in the Gravity
Research Foundation Essay Contest, 2005; to appear in the special issue of
IJMP
Post-Newtonian Freely Specifiable Initial Data for Binary Black Holes in Numerical Relativity
Construction of astrophysically realistic initial data remains a central
problem when modelling the merger and eventual coalescence of binary black
holes in numerical relativity. The objective of this paper is to provide
astrophysically realistic freely specifiable initial data for binary black hole
systems in numerical relativity, which are in agreement with post-Newtonian
results. Following the approach taken by Blanchet, we propose a particular
solution to the time-asymmetric constraint equations, which represent a system
of two moving black holes, in the form of the standard conformal decomposition
of the spatial metric and the extrinsic curvature. The solution for the spatial
metric is given in symmetric tracefree form, as well as in Dirac coordinates.
We show that the solution differs from the usual post-Newtonian metric up to
the 2PN order by a coordinate transformation. In addition, the solutions,
defined at every point of space, differ at second post-Newtonian order from the
exact, conformally flat, Bowen-York solution of the constraints.Comment: 41 pages, no figures, accepted for publication in Phys. Rev. D,
significant revision in presentation (including added references and
corrected typos
Gravity in Brans-Dicke theory with Born-Infeld scalar field and the Pioneer anomaly
In this paper we discuss a model which can be considered as a generalization
of the well-known scalar-tensor Brans-Dicke theory. This model possesses an
interesting feature: due to Born-Infeld type non-linearity of the scalar field
the properties of the interaction between two test bodies depend significantly
on their masses. It is shown that the model can be interesting in view of the
Pioneer 10, 11 spacecraft anomaly.Comment: 10 pages, 1 figure, partially changed conten
Binary Black Hole Coalescence in Semi-Analytic Puncture Evolution
Binary black-hole coalescence is treated semi-analytically by a novel
approach. Our prescription employs the conservative Skeleton Hamiltonian that
describes orbiting Brill-Lindquist wormholes (termed punctures in Numerical
Relativity) within a waveless truncation to the Einstein field equations [G.
Faye, P. Jaranowski and G. Sch\"afer, Phys. Rev. D {\bf 69}, 124029 (2004)]. We
incorporate, in a transparent Hamiltonian way and in Burke-Thorne gauge
structure, the effects of gravitational radiation reaction into the above
Skeleton dynamics with the help of 3.5PN accurate angular momentum flux for
compact binaries in quasi-circular orbits to obtain a Semi-Analytic Puncture
Evolution to model merging black-hole binaries. With the help of the TaylorT4
approximant at 3.5PN order, we perform a {\it first-order} comparison between
gravitational wave phase evolutions in Numerical Relativity and our approach
for equal-mass binary black holes. This comparison reveals that a modified
Skeletonian reactive dynamics that employs flexible parameters will be required
to prevent the dephasing between our scheme and Numerical Relativity, similar
to what is pursued in the Effective One Body approach. A rough estimate for the
gravitational waveform associated with the binary black-hole coalescence in our
approach is also provided.Comment: 16 pages, 5 figure
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