34 research outputs found
Three-charge 2J black ring
Using recently proposed new solution generating technique, we construct the
charged version of Pomeranski-Senkov doubly rotating black ring in the
five-dimensional supergravity. For arbitrary values of charges the solution is
unbalanced, but the Dirac-Misner string is removed when two of the charges are
set to zero. In this particular case our solution can be uplifted to some
solution of six-dimensional vacuum gravity.Comment: 9 pages revtex
Improved generating technique for D=5 supergravities and squashed Kaluza-Klein Black Holes
Recently we suggested a solution generating technique for five-dimensional
supergravity with three Abelian vector fields based on the hidden SO(4,4)
symmetry of the three-dimensionally reduced theory. This technique generalizes
the generating technique developed earlier for minimal 5D
supergravity (A. Bouchareb, G. Cl\'ement, C-M. Chen, D. V. Gal'tsov, N. G.
Scherbluk, and Th. Wolf, Phys. Rev. D {\bf 76}, 104032 (2007)) and provides a
new matrix representation for cosets forming the corresponding sigma-models in
both cases. Here we further improve these methods introducing a matrix-valued
dualisation procedure which helps to avoid difficulties associated with solving
the dualisation equations in the component form. This new approach is used to
generate a five-parametric rotating charged Kaluza-Klein black hole with the
squashed horizon adding one parameter more to the recent solution by Tomizawa,
Yasui and Morisawa which was constructed using the previous version of the
generating technique.Comment: 20 pages, revtex
Cylindrically symmetric solitons in Einstein-Yang-Mills theory
Recently new Einstein-Yang-Mills (EYM) soliton solutions were presented which
describe superconducting strings with Kasner asymptotic (hep-th/0610183). Here
we study the static cylindrically symmetric SU(2) EYM system in more detail.
The ansatz for the gauge field corresponds to superposition of the azimuthal
and the longitudinal components of the color magnetic field. We
derive sum rules relating data on the symmetry axis to asymptotic data and show
that generic asymptotic structure of regular solutions is Kasner. Solutions
starting with vacuum data on the axis generically are divergent. Regular
solutions correspond to some bifurcation manifold in the space of parameters
which has the low-energy limiting point corresponding to string solutions in
flat space (with the divergent total energy) and the high-curvature point where
gravity is crucial. Some analytical results are presented for the low energy
limit, and numerical bifurcation curves are constructed in the gravitating
case. Depending on the parameters, the solution looks like a straight string or
a pair of straight and circular strings. The existence of such non-linear
superposition of two strings becomes possible due to self-interaction terms in
the Yang-Mills action which suppress contribution of the circular string near
the polar axis.Comment: 21 pages, 11 figure
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
Extremal dyonic black holes in D=4 Gauss-Bonnet gravity
We investigate extremal dyon black holes in the Einstein-Maxwell-dilaton
(EMD) theory with higher curvature corrections in the form of the Gauss-Bonnet
density coupled to the dilaton. In the same theory without the Gauss-Bonnet
term the extremal dyon solutions exist only for discrete values of the dilaton
coupling constant . We show that the Gauss-Bonnet term acts as a dyon hair
tonic enlarging the allowed values of to continuous domains in the plane
the second parameter being the magnetic charge. In the limit of the
vanishing curvature coupling (a large magnetic charge) the dyon solutions
obtained tend to the Reissner-Nordstr\"om solution but not to the extremal
dyons of the EMD theory. Both solutions have the same values of the horizon
radius as a function of charges. The entropy of new dyonic black holes
interpolates between the Bekenstein-Hawking value in the limit of the large
magnetic charge (equivalent to the vanishing Gauss-Bonnet coupling) and twice
this value for the vanishing magnetic charge. Although an expression for the
entropy can be obtained analytically using purely local near-horizon solutions,
its interpretation as the black hole entropy is legitimate only once the global
black hole solution is known to exist, and we obtain numerically the
corresponding conditions on the parameters. Thus, a purely local analysis is
insufficient to fully understand the entropy of the curvature corrected black
holes. We also find dyon solutions which are not asymptotically flat, but
approach the linear dilaton background at infinity. They describe magnetic
black holes on the electric linear dilaton background.Comment: 19 pages, 3 figures, revtex
All extremal instantons in Einstein-Maxwell-dilaton-axion theory
We construct explicitly all extremal instanton solutions to supergravity truncated to one vector field (Einstein-Maxwell-dilaton-axion
(EMDA) theory). These correspond to null geodesics of the target space of the
sigma-model obtained by
compactification of four-dimensional Euclidean EMDA on a circle. They satisfy a
no-force condition in terms of the asymptotic charges and part of them
(corresponding to nilpotent orbits of the U-duality) are
presumably supersymmetric. The space of finite action solutions is found to be
unexpectedly large and includes, besides the Euclidean versions of known
Lorentzian solutions, a number of new asymptotically locally flat (ALF)
instantons endowed with electric, magnetic, dilaton and axion charges. We also
describe new classes of charged asymptotically locally Euclidean (ALE)
instantons as well as some exceptional solutions. Our classification scheme is
based on the algebraic classification of matrix generators according to their
rank, according to the nature of the charge vectors and according to the number
of independent harmonic functions with unequal charges. Besides the nilpotent
orbits of , we find solutions which satisfy the asymptotic no-force
condition, but are not supersymmetric. The renormalized on-shell action for
instantons is calculated using the method of matched background subtraction.Comment: 59 pages, revtex
Generating technique for supergravity
We develop generating technique for solutions of supergravity via
dimensional reduction to three dimensions. This theory, which recently
attracted attention in connection with black rings, can be viewed as consistent
truncation of the compactification of the eleven-dimensional
supergravity. Its further reduction to three dimensions accompanied by
dualisation of the vector fields leads to 3D gravity coupled sigma model on the
homogeneous space or depending on the signature of the three-space. We construct a matrix representation of these cosets in terms of lower-dimensional blocks.
Using it we express solution generating transformations in terms of the
potentials and identify those preserving asymptotic conditions relevant to
black holes and black rings. As an application, we derive the doubly rotating
black hole solution with three independent charges. A suitable contraction of
the above cosets is used to construct a new representation of the coset
relevant for minimal five-dimensional
supergravity.Comment: A typo in Sec. VII B corrected, some references adde
Bertotti-Robinson type solutions to Dilaton-Axion Gravity
We present a new solution to dilaton-axion gravity which looks like a
rotating Bertotti-Robinson (BR) Universe. It is supported by an homogeneous
Maxwell field and a linear axion and can be obtained as a near-horizon limit of
extremal rotating dilaton-axion black holes. It has the isometry where U(1) is the remnant of the SO(3) symmetry of BR broken by rotation,
while corresponds to the sector which no longer factors out
of the full spacetime. Alternatively our solution can be obtained from the D=5
vacuum counterpart to the dyonic BR with equal electric and magnetic field
strengths. The derivation amounts to smearing it in D=6 and then reducing to
D=4 with dualization of one Kaluza-Klein two-form in D=5 to produce an axion.
Using a similar dualization procedure, the rotating BR solution is uplifted to
D=11 supergravity. We show that it breaks all supersymmetries of N=4
supergravity in D=4, and that its higher dimensional embeddings are not
supersymmetric either. But, hopefully it may provide a new arena for corformal
mechanics and holography. Applying a complex coordinate transformation we also
derive a BR solution endowed with a NUT parameter.Comment: 21 page
Linear dilaton black holes
We present new solutions to Einstein-Maxwell-dilaton-axion (EMDA) gravity in
four dimensions describing black holes which asymptote to the linear dilaton
background. In the non-rotating case they can be obtained as the limiting
geometry of dilaton black holes. The rotating solutions (possibly endowed with
a NUT parameter) are constructed using a generating technique based on the
Sp(4,R) duality of the EMDA system. In a certain limit (with no event horizon
present) our rotating solutions coincide with supersymmetric
Israel-Wilson-Perjes type dilaton-axion solutions. In presence of an event
horizon supersymmetry is broken. The temperature of the static black holes is
constant, and their mass does not depend on it, so the heat capacity is zero.
We investigate geodesics and wave propagation in these spacetimes and find
superradiance in the rotating case. Because of the non-asymptotically flat
nature of the geometry, certain modes are reflected from infinity, in
particular, all superradiant modes are confined. This leads to classical
instability of the rotating solutions. The non-rotating linear dilaton black
holes are shown to be stable under spherical perturbations.Comment: 30 pages, 1 eps figure, 8 typos correcte
Gravitational and dilaton radiation from a relativistic membrane
Recent scenarios of the TeV-scale brane cosmology suggest a possibility of
existence in the early universe of two-dimensional topological defects:
relativistic membranes. Like cosmic strings, oscillating membranes could emit
gravitational radiation contributing to a stochastic background of
gravitational waves. We calculate dilaton and gravitational radiation from a
closed toroidal membrane excited along one homology cycle. The spectral-angular
distributions of dilaton and gravitational radiation are obtained in a closed
form in terms of Bessel's functions. The angular distributions are affected by
oscillating factors due to an interference of radiation from different segments
of the membrane. The dilaton radiation power is dominated by a few lower
harmonics of the basic frequency, while the spectrum of the gravitational
radiation contains also a substantial contribution from higher harmonics. The
radiative lifetime of the membrane is determined by its tension and depends
weakly on the ratio of two radii of the torus. Qualitatively it is equal to the
ratio of the membrane area at the maximal extension to the gravitational radius
of the membrane as a whole.Comment: Latex error corrected (Fig.1 was called twice instead of Fig.4),
minor edits. Revtex4, 9 pages, 8 eps figure