140 research outputs found
S-Duality at the Black Hole Threshold in Gravitational Collapse
We study gravitational collapse of the axion/dilaton field in classical low
energy string theory, at the threshold for black hole formation. A new critical
solution is derived that is spherically symmetric and continuously
self-similar. The universal scaling and echoing behavior discovered by Choptuik
in gravitational collapse appear in a somewhat different form. In particular,
echoing takes the form of SL(2,R) rotations (cf. S-duality). The collapse
leaves behind an outgoing pulse of axion/dilaton radiation, with nearly but not
exactly flat spacetime within it.Comment: 8 pages of LaTeX, uses style "revtex"; 1 figure, available in
archive, or at ftp://ftp.itp.ucsb.edu/figures/nsf-itp-95-15.ep
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
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
Leghennenhouderij in diep dal
De leghennenhouders ontvangen nu al twee jaar eierprijzen fors onder de kostprijs. Vooral scharrelhennenhouders hebben moeite het hoofd boven water te houden. Het perspectief voor het komende halfjaar is niet gunstig
Beyond the Singularity of the 2-D Charged Black Hole
Two dimensional charged black holes in string theory can be obtained as exact
(SL(2,R)xU(1))/U(1) quotient CFTs. The geometry of the quotient is induced from
that of the group, and in particular includes regions beyond the black hole
singularities. Moreover, wavefunctions in such black holes are obtained from
gauge invariant vertex operators in the SL(2,R) CFT, hence their behavior
beyond the singularity is determined. When the black hole is charged we find
that the wavefunctions are smooth at the singularities. Unlike the uncharged
case, scattering waves prepared beyond the singularity are not fully reflected;
part of the wave is transmitted through the singularity. Hence, the physics
outside the horizon of a charged black hole is sensitive to conditions set
behind the past singularity.Comment: 19 pages, 5 figures; v2: refs added, minor typos corrected; v3:
references on the infinite blue shift at the inner horizon and minor
corrections adde
Non-Singularity of the Exact Two-Dimensional String Black Hole
We study the global structure of the exact two-dimensional space-time which
emerges from string theory. Previous work has shown that in the semi-classical
limit, this is a black hole similar to the Schwarzschild solution. However, we
find that in the exact case, a new Euclidean region appears "between" the
singularity and black hole interior. However the boundary between the
Lorentzian and Euclidean regions is a coordinate singularity, which turns out
to be a surface of time reflection symmetry in an extended space-time. Thus
strings having fallen through the black hole horizon would eventually emerge
through another one into a new asymptotically flat region. The maximally
extended space-time consists of an infinite number of universes connected by
wormholes. There are no singularities present in this geometry. We also
calculate the mass and temperature associated with the space-time.Comment: 9 pages, latex, DAMTP R93/
Black-Hole-Wave Duality in String Theory
Extreme 4-dimensional dilaton black holes embedded into 10-dimensional
geometry are shown to be dual to the gravitational waves in string theory. The
corresponding gravitational waves are the generalization of pp-fronted waves,
called supersymmetric string waves. They are given by Brinkmann metric and the
two-form field, without a dilaton. The non-diagonal part of the metric of the
dual partner of the wave together with the two-form field correspond to the
vector field in 4-dimensional geometry of the charged extreme black holes.Comment: 12 pages, LaTeX, preprint UG-3/94, SU-ITP-94-11, QMW-PH-94-1
Stationary Black Holes with Static and Counterrotating Horizons
We show that rotating dyonic black holes with static and counterrotating
horizon exist in Einstein-Maxwell-dilaton theory when the dilaton coupling
constant exceeds the Kaluza-Klein value. The black holes with static horizon
bifurcate from the static black holes. Their mass decreases with increasing
angular momentum, their horizons are prolate.Comment: 4 pages, 6 figure
New perturbative solutions of the Kerr-Newman dilatonic black hole field equations
This work describes new perturbative solutions to the classical,
four-dimensional Kerr--Newman dilaton black hole field equations. Our solutions
do not require the black hole to be slowly rotating. The unperturbed solution
is taken to be the ordinary Kerr solution, and the perturbation parameter is
effectively the square of the charge-to-mass ratio of the
Kerr--Newman black hole. We have uncovered a new, exact conjugation (mirror)
symmetry for the theory, which maps the small coupling sector to the strong
coupling sector (). We also calculate the gyromagnetic ratio of
the black hole.Comment: Revtex, 27 page
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