35 research outputs found
Charged Dilaton Black Holes with a Cosmological Constant
The properties of static spherically symmetric black holes, which are either
electrically or magnetically charged, and which are coupled to the dilaton in
the presence of a cosmological constant, are considered. It is shown that such
solutions do not exist if the cosmological constant is positive (in arbitrary
spacetime dimension >= 4). However, asymptotically anti-de Sitter black hole
solutions with a single horizon do exist if the cosmological constant is
negative. These solutions are studied numerically in four dimensions and the
thermodynamic properties of the solutions are derived. The extreme solutions
are found to have zero entropy and infinite temperature for all non-zero values
of the dilaton coupling constant.Comment: 12 pages, epsf, phyzzx, 4 in-text figures incl. (minor typos fixed, 1
reference added
Wavy Strings: Black or Bright?
Recent developments in string theory have brought forth a considerable
interest in time-dependent hair on extended objects. This novel new hair is
typically characterized by a wave profile along the horizon and angular
momentum quantum numbers in the transverse space. In this work, we
present an extensive treatment of such oscillating black objects, focusing on
their geometric properties. We first give a theorem of purely geometric nature,
stating that such wavy hair cannot be detected by any scalar invariant built
out of the curvature and/or matter fields. However, we show that the tidal
forces detected by an infalling observer diverge at the `horizon' of a black
string superposed with a vibration in any mode with . The same
argument applied to longitudinal () waves detects only finite tidal
forces. We also provide an example with a manifestly smooth metric, proving
that at least a certain class of these longitudinal waves have regular
horizons.Comment: 45 pages, latex, no figure
A Charged Rotating Black Ring
We construct a supergravity solution describing a charged rotating black ring
with S^2xS^1 horizon in a five dimensional asymptotically flat spacetime. In
the neutral limit the solution is the rotating black ring recently found by
Emparan and Reall. We determine the exact value of the lower bound on J^2/M^3,
where J is the angular momentum and M the mass; the black ring saturating this
bound has maximum entropy for the given mass. The charged black ring is
characterized by mass M, angular momentum J, and electric charge Q, and it also
carries local fundamental string charge. The electric charge distributed
uniformly along the ring helps support the ring against its gravitational
self-attraction, so that J^2/M^3 can be made arbitrarily small while Q/M
remains finite. The charged black ring has an extremal limit in which the
horizon coincides with the singularity.Comment: 25 pages, 1 figur
Exact Primordial Black Strings in Four Dimensions
A solution of effective string theory in four dimensions is presented which
admits interpretation of a rotating black cosmic string. It is constructed by
tensoring the three dimensional black hole, extended with the Kalb-Ramond
axion, with a flat direction. The physical interpretation of the solution is
discussed, with special attention on the axion, which is found to play a role
very similar to a Higgs field. Finally, it is pointed out that the solution
represents an exact WZWN model on the string world sheet, to all
orders in the inverse string tension .Comment: 11 pages plain TeX, Univ. of Alberta preprint Alberta-THY-14-199
Black Rings, Supertubes, and a Stringy Resolution of Black Hole Non-Uniqueness
In order to address the issues raised by the recent discovery of
non-uniqueness of black holes in five dimensions, we construct a solution of
string theory at low energies describing a five-dimensional spinning black ring
with three charges that can be interpreted as D1-brane, D5-brane, and momentum
charges. The solution possesses closed timelike curves (CTCs) and other
pathologies, whose origin we clarify. These pathologies can be avoided by
setting any one of the charges, e.g. the momentum, to zero. We argue that the
D1-D5-charged black ring, lifted to six dimensions, describes the thermal
excitation of a supersymmetric D1-D5 supertube, which is in the same U-duality
class as the D0-F1 supertube. We explain how the stringy microscopic
description of the D1-D5 system distinguishes between a spherical black hole
and a black ring with the same asymptotic charges, and therefore provides a
(partial) resolution of the non-uniqueness of black holes in five dimensions.Comment: 33 pages, 1 figur
On Some New Black String Solutions in Three Dimensions
We derive several new solutions in three-dimensional stringy gravity. The
solutions are obtained with the help of string duality transformations. They
represent stationary configurations with horizons, and are surrounded by
(quasi) topologically massive Abelian gauge hair, in addition to the dilaton
and the Kalb-Ramond axion. Our analysis suggests that there exists a more
general family, where our solutions are special limits. Finally, we use the
generating technique recently proposed by Garfinkle to construct a traveling
wave on the extremal variant of one of our solutions.Comment: revtex, 38 pages including 3 figure
New solutions in 3D gravity
We study gravitational theory in 1+2 spacetime dimensions which is determined
by the Lagrangian constructed as a sum of the Einstein-Hilbert term plus the
two (translational and rotational) gravitational Chern-Simons terms. When the
corresponding coupling constants vanish, we are left with the purely Einstein
theory of gravity. We obtain new exact solutions for the gravitational field
equations with the nontrivial material sources. Special attention is paid to
plane-fronted gravitational waves (in case of the Maxwell field source) and to
the circularly symmetric as well as the anisotropic cosmological solutions
which arise for the ideal fluid matter source.Comment: Revtex, 21 pages, no figure
Mass Spectrum of Strings in Anti de Sitter Spacetime
We perform string quantization in anti de Sitter (AdS) spacetime. The string
motion is stable, oscillatory in time with real frequencies and the string size and energy are bounded. The
string fluctuations around the center of mass are well behaved. We find the
mass formula which is also well behaved in all regimes. There is an {\it
infinite} number of states with arbitrarily high mass in AdS (in de Sitter (dS)
there is a {\it finite} number of states only). The critical dimension at which
the graviton appears is as in de Sitter space. A cosmological constant
(whatever its sign) introduces a {\it fine structure} effect
(splitting of levels) in the mass spectrum at all states beyond the graviton.
The high mass spectrum changes drastically with respect to flat Minkowski
spacetime. For {\it
independent} of and the level spacing {\it grows} with the
eigenvalue of the number operator, The density of states grows
like \mbox{Exp}[(m/\sqrt{\mid\Lambda\mid}\;)^{1/2}] (instead of
\rho(m)\sim\mbox{Exp}[m\sqrt{\alpha'}] as in Minkowski space), thus {\it
discarding} the existence of a critical string temperature.
For the sake of completeness, we also study the quantum strings in the black
string background, where strings behave, in many respects, as in the ordinary
black hole backgrounds. The mass spectrum is equal to the mass spectrum in flat
Minkowski space.Comment: 31 pages, Latex, DEMIRM-Paris-9404
Four-dimensional anti-de Sitter black holes from a three-dimensional perspective: Full complexity
The dimensional reduction of black hole solutions in four-dimensional (4D)
general relativity is performed and new 3D black hole solutions are obtained.
Considering a 4D spacetime with one spacelike Killing vector, it is possible to
split the Einstein-Hilbert-Maxwell action with a cosmological term in terms of
3D quantities. Definitions of quasilocal mass and charges in 3D spacetimes are
reviewed. The analysis is then particularized to the toroidal charged rotating
anti-de Sitter black hole. The reinterpretation of the fields and charges in
terms of a three-dimensional point of view is given in each case, and the
causal structure analyzed.Comment: 26 pages, 1 figure, Uses revtex
Higher Dimensional Charged Rotating Dilaton Black Holes
In this paper, we present the metric for the -dimensional charged slowly
rotating dilaton black hole with independent rotation
parameters, associated with orthogonal planes of rotation in the background
of asymptotically flat and asymptotically (anti)-de Sitter spacetime. The mass,
angular momentum and the gyromagnetic ratio of such a black hole are determined
for the arbitrary values of the dilaton coupling constant. We find that the
gyromagnetic ratio crucially depends on the dilaton coupling constant,
, and decreases with increasing in any dimension.Comment: 15 pages, 1 figur