41 research outputs found
Dyonic dilaton black holes
The properties of static spherically symmetric black holes, which are both
electrically and magnetically charged, and which are coupled to the dilaton in
the presence of a cosmological constant, Lambda, are considered. It is shown
that apart from the Reissner-Nordstrom-de Sitter solution with constant
dilaton, such solutions do not exist if Lambda > 0 (in arbitrary spacetime
dimension >=4 ). However, asymptotically anti-de Sitter dyonic black hole
solutions with a non-trivial dilaton do exist if Lambda < 0. Both these
solutions and the asymptotically flat (Lambda = 0) solutions are studied
numerically for arbitrary values of the dilaton coupling parameter, g_0, in
four dimensions. The asymptotically flat solutions are found to exhibit two
horizons if g_0 = 0, 1, \sqrt{3}, \sqrt{6}, ..., \sqrt{n(n+1)/2},..., and one
horizon otherwise. For asymptotically anti-de Sitter solutions the result is
similar, but the corresponding values of g_0 are altered in a non-linear
fashion which depends on Lambda and the mass and charges of the black holes.
All dyonic solutions with Lambda <= 0 are found to have zero Hawking
temperature in the extreme limit, however, regardless of the value of g_0.Comment: 24 pages, phyzzx, epsf, 7 in-text figures. Small addition to
introduction, and a few extra reference
Rotating Dilaton Black Holes
It is shown that an arbitrarily small amount of angular momentum can
qualitatively change the properties of extremal charged black holes coupled to
a dilaton. In addition, the gyromagnetic ratio of these black holes is computed
and an exact rotating black string solution is presented.Comment: 14 page
All the Four Dimensional Static, Spherically Symmetric Solutions of Abelian Kaluza-Klein Theory
We present the explicit form for all the four dimensional, static,
spherically symmetric solutions in -d Abelian Kaluza-Klein theory by
performing a subset of transformations corresponding to four
boosts on the Schwarzschild solution, supplemented by
transformations. The solutions are parameterized by the mass , Taub-Nut
charge , electric and magnetic
charges. Non-extreme black holes (with zero Taub-NUT charge) have either the
Reissner-Nordstr\" om or Schwarzschild global space-time. Supersymmetric
extreme black holes have a null or naked singularity, while non-supersymmetric
extreme ones have a global space-time of extreme Reissner-Nordstr\" om black
holes.Comment: 8 pages, uses RevTex, improved version to appear in Phys. Rev. Let
STATIC FOUR-DIMENSIONAL ABELIAN BLACK HOLES IN KALUZA-KLEIN THEORY
Static, four-dimensional (4-d) black holes (BH's) in ()-d Kaluza-Klein
(KK) theory with Abelian isometry and diagonal internal metric have at most one
electric () and one magnetic () charges, which can either come from the
same -gauge field (corresponding to BH's in effective 5-d KK theory) or
from different ones (corresponding to BH's with isometry
of an effective 6-d KK theory). In the latter case, explicit non-extreme
solutions have the global space-time of Schwarzschild BH's, finite temperature,
and non-zero entropy. In the extreme (supersymmetric) limit the singularity
becomes null, the temperature saturates the upper bound
, and entropy is zero. A class of KK BH's with
constrained charge configurations, exhibiting a continuous electric-magnetic
duality, are generated by global transformations on the above classes
of the solutions.Comment: 11 pages, 2 Postscript figures. uses RevTeX and psfig.sty (for figs)
paper and figs also at ftp://dept.physics.upenn.edu/pub/Cvetic/UPR-645-
Black holes in supergravity and integrability
Stationary black holes of massless supergravity theories are described by
certain geodesic curves on the target space that is obtained after dimensional
reduction over time. When the target space is a symmetric coset space we make
use of the group-theoretical structure to prove that the second order geodesic
equations are integrable in the sense of Liouville, by explicitly constructing
the correct amount of Hamiltonians in involution. This implies that the
Hamilton-Jacobi formalism can be applied, which proves that all such black hole
solutions, including non-extremal solutions, possess a description in terms of
a (fake) superpotential. Furthermore, we improve the existing integration
method by the construction of a Lax integration algorithm that integrates the
second order equations in one step instead of the usual two step procedure. We
illustrate this technology with a specific example.Comment: 44 pages, small typos correcte
Inverse dualisation and non-local dualities between Einstein gravity and supergravities
We investigate non-local dualities between suitably compactified
higher-dimensional Einstein gravity and supergravities which can be revealed if
one reinterprets the dualised Kaluza-Klein two-forms in as antisymmetric
forms belonging to supergravities. We find several examples of such a
correspondence including one between the six-dimensional Einstein gravity and
the four-dimensional Einstein-Maxwell-dilaton-axion theory (truncated N=4
supergravity), and others between the compactified eleven and ten-dimensional
supergravities and the eight or ten-dimensional pure gravity. The Killing
spinor equation of the D=11 supergravity is shown to be equivalent to the
geometric Killing spinor equation in the dual gravity. We give several examples
of using new dualities for solution generation and demonstrate how -branes
can be interpreted as non-local duals of pure gravity solutions. New
supersymmetric solutions are presented including -brane with two
rotation parameters.Comment: 32 pages, Late
Pair Creation of Dilaton Black Holes
We consider dilaton gravity theories in four spacetime dimensions
parametrised by a constant , which controls the dilaton coupling, and
construct new exact solutions. We first generalise the C-metric of
Einstein-Maxwell theory () to solutions corresponding to oppositely
charged dilaton black holes undergoing uniform acceleration for general . We
next develop a solution generating technique which allows us to ``embed" the
dilaton C-metrics in magnetic dilaton Melvin backgrounds, thus generalising the
Ernst metric of Einstein-Maxwell theory. By adjusting the parameters
appropriately, it is possible to eliminate the nodal singularities of the
dilaton C-metrics. For (but not for ), it is possible to further
restrict the parameters so that the dilaton Ernst solutions have a smooth
euclidean section with topology , corresponding to
instantons describing the pair production of dilaton black holes in a magnetic
field. A different restriction on the parameters leads to smooth instantons for
all values of with topology .Comment: 22 pages, EFI-93-51, FERMILAB-Pub-93/272-A, UMHEP-393. (Asymptotics
of Ernst solutions clarified, typos repaired
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
Moduli and (un)attractor black hole thermodynamics
We investigate four-dimensional spherically symmetric black hole solutions in
gravity theories with massless, neutral scalars non-minimally coupled to gauge
fields. In the non-extremal case, we explicitly show that, under the variation
of the moduli, the scalar charges appear in the first law of black hole
thermodynamics. In the extremal limit, the near horizon geometry is
and the entropy does not depend on the values of moduli at
infinity. We discuss the attractor behaviour by using Sen's entropy function
formalism as well as the effective potential approach and their relation with
the results previously obtained through special geometry method. We also argue
that the attractor mechanism is at the basis of the matching between the
microscopic and macroscopic entropies for the extremal non-BPS Kaluza-Klein
black hole.Comment: 36 pages, no figures, V2: minor changes, misprints corrected,
expanded references; V3: sections 4.3 and 4.5 added; V4: minor changes,
matches the published versio
Generalized Weyl Solutions
It was shown by Weyl that the general static axisymmetric solution of the
vacuum Einstein equations in four dimensions is given in terms of a single
axisymmetric solution of the Laplace equation in three-dimensional flat space.
Weyl's construction is generalized here to arbitrary dimension . The
general solution of the D-dimensional vacuum Einstein equations that admits D-2
orthogonal commuting non-null Killing vector fields is given either in terms of
D-3 independent axisymmetric solutions of Laplace's equation in
three-dimensional flat space or by D-4 independent solutions of Laplace's
equation in two-dimensional flat space. Explicit examples of new solutions are
given. These include a five-dimensional asymptotically flat ``black ring'' with
an event horizon of topology S^1 x S^2 held in equilibrium by a conical
singularity in the form of a disc.Comment: 50 pages, 10 figures; v2: minor improvement