2,887 research outputs found
Oxidation of D=3 cosets and Bonnor dualities in
Bonnor's map in General Relativity is duality between (dimensionally reduced)
vacuum gravity and static truncation of electro-vacuum theory. It was used as a
tool to generate an exact solution of electro-vacuum from some vacuum solution.
It can be expected that similar dualities will be useful for solution
generation in higher-dimensional theories too. Here we study such maps within a
class of theories in dimensions using oxidation of D=3 cosets and
consistent truncation of the corresponding theories. Our class includes those
theories whose D=3 symmetries are subgroups of . It contains
six-dimensional minimal supergravity, five-dimensional minimal and
supergravities and a number of four-dimensional theories which attracted
attention recently in the search of exact solutions. We give explicit
reduction/truncation formulas relating different theories in dimensions in terms of metrics and matter fields and discuss various alternative
duality chains between them.Comment: Two references added, Introduction slightly edited, mispints removed.
Journal versio
Black branes on the linear dilaton background
We show that the complete static black p-brane supergravity solution with a
single charge contains two and only two branches with respect to behavior at
infinity in the transverse space. One branch is the standard family of
asymptotically flat black branes, and another is the family of black branes
which asymptotically approach the linear dilaton background with antisymmetric
form flux (LDB). Such configurations were previously obtained in the
near-horizon near-extreme limit of the dilatonic asymptotically flat p-branes,
and used to describe the thermal phase of field theories involved in the DW/QFT
dualities and the thermodynamics of little string theory in the case of the
NS5-brane. Here we show by direct integration of the Einstein equations that
the asymptotically LDB p-branes are indeed exact supergravity solutions, and we
prove a new uniqueness theorem for static p-brane solutions satisfying cosmic
censorship. In the non-dilatonic case, our general non-asymptotically flat
p-branes are uncharged black branes on the background supported by the form flux. We develop the general formalism of
quasilocal quantities for non-asymptotically flat supergravity solutions with
antisymmetric form fields, and show that our solutions satisfy the first law of
theormodynamics. We also suggest a constructive procedure to derive rotating
asymptotically LDB brane solutions.Comment: 16 pages, revtex4, v2 - references added, "authors" metatag correcte
Bertotti-Robinson solutions of D=5 Einstein-Maxwell-Chern-Simons-Lambda theory
We present a series of new solutions in five-dimensional
Einstein-Maxwell-Chern-Simons theory with an arbitrary Chern-Simons coupling
and a cosmological constant . For general and
we give various generalizations of the Bertotti-Robinson solutions
supported by electric and magnetic fluxes, some of which presumably describe
the near-horizon regions of black strings or black rings. Among them there is a
solution which could apply to the horizon of a topological AdS black ring in
gauged minimal supergravity. Others are horizonless and geodesically complete.
We also construct extremal asymptotically flat multi-string solutions for
and arbitrary .Comment: 17 pages, revtex
Dyonic Wormholes in 5D Kaluza-Klein Theory
New spherically symmetric dyonic solutions, describing a wormhole-like class
of spacetime configurations in five-dimensional Kaluza-Klein theory, are given
in an explicit form. For this type of solution the electric and magnetic fields
cause a significantly different global structure. For the electric dominated
case, the solution is everywhere regular but, when the magnetic strength
overcomes the electric contribution, the mouths of the wormhole become singular
points. When the electric and magnetic charge parameters are identical, the
throats ``degenerate'' and the solution reduces to the trivial embedding of the
four-dimensional massless Reissner-Nordstr{\"o}m black hole solution. In
addition, their counterparts in eleven-dimensional supergravity are constructed
by a non-trivial uplifting.Comment: Revised version to appear in Class. Quant. Gra
Behaviour laws of households in term of location and consumtion of their dwelling
The aim of this report is to give some explanation about the behaviour laws ofthe households in term of location and consumption of their dwelling, in anurban area (city of Lyon, France) . The location is considered here in relationwith the choice of removing and the choice of the dwelling . We try to valid theassertions we present by data collected in different surveys . The work is basedon a revealedpreferences survey, carried out in1997,concerning752households
Black hole mass and angular momentum in 2+1 gravity
We propose a new definition for the mass and angular momentum of neutral or
electrically charged black holes in 2+1 gravity with two Killing vectors. These
finite conserved quantities, associated with the SL(2,R) invariance of the
reduced mechanical system, are shown to be identical to the quasilocal
conserved quantities for an improved gravitational action corresponding to
mixed boundary conditions. They obey a general Smarr-like formula and, in all
cases investigated, are consistent with the first law of black hole
thermodynamics. Our framework is applied to the computation of the mass and
angular momentum of black hole solutions to several field-theoretical models.Comment: 23 pages, 3 references added, to be published in Physical Review
Anderson Localization of Expanding Bose-Einstein Condensates in Random Potentials
We show that the expansion of an initially confined interacting 1D
Bose-Einstein condensate can exhibit Anderson localization in a weak random
potential with correlation length \sigma_R. For speckle potentials the Fourier
transform of the correlation function vanishes for momenta k > 2/\sigma_R so
that the Lyapunov exponent vanishes in the Born approximation for k >
1/\sigma_R. Then, for the initial healing length of the condensate \xi >
\sigma_R the localization is exponential, and for \xi < \sigma_R it changes to
algebraic.Comment: published versioon (no significant change compared to last version
Kaluza-Klein and Gauss-Bonnet cosmic strings
We make a systematic investigation of stationary cylindrically symmetric
solutions to the five-dimensional Einstein and Einstein-Gauss-Bonnet equations.
Apart from the five-dimensional neutral cosmic string metric, we find two new
exact solutions which qualify as cosmic strings, one corresponding to an
electrically charged cosmic string, the other to an extended superconducting
cosmic string surrounding a charged core. In both cases, test particles are
deflected away from the singular line source. We extend both kinds of solutions
to exact multi-cosmic string solutions.Comment: 26 pages, LaTex, no figure
Ring Wormholes in D-Dimensional Einstein and Dilaton Gravity
On the basis of exact solutions to the Einstein-Abelian gauge-dilaton
equations in -dimensional gravity, the properties of static axial
configurations are discussed. Solutions free of curvature singularities are
selected; they can be attributed to traversible wormholes with cosmic
string-like singularities at their necks. In the presence of an electromagnetic
field some of these wormholes are globally regular, the string-like singularity
being replaced by a set of twofold branching points. Consequences of wormhole
regularity and symmetry conditions are discussed. In particular, it is shown
that (i) regular, symmetric wormholes have necessarily positive masses as
viewed from both asymptotics and (ii) their characteristic length scale in the
big charge limit () is of the order of the ``classical radius"
.Comment: Latex file, 15 page
Analytical treatment of critical collapse in 2+1 dimensional AdS spacetime: a toy model
We present an exact collapsing solution to 2+1 gravity with a negative
cosmological constant minimally coupled to a massless scalar field, which
exhibits physical properties making it a candidate critical solution. We
discuss its global causal structure and its symmetries in relation with those
of the corresponding continously self-similar solution derived in the
case. Linear perturbations on this background lead to approximate
black hole solutions. The critical exponent is found to be .Comment: 22 pages, 6 figures. Major changes in the discussions of Sects. 2 and
5. The value of the critical exponent has been revised to \gamma = 2/
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