351 research outputs found
Black Holes and Flop Transitions in M-Theory on Calabi-Yau Threefolds
We present fivedimensional extreme black hole solutions of M-theory
compactified on Calabi-Yau threefolds and study these solutions in the context
of flop transitions in the extended Kahler cone. In particular we consider a
specific model and present black hole solutions, breaking half of N=2
supersymmetry, in two regions of the extended Kahler cone, which are connected
by a flop transition. The conditions necessary to match both solutions at the
flop transition are analysed. Finally we also discuss the conditions to obtain
massless black holes at the flop transition.Comment: 19 pp, LaTe
Consistent reductions of IIB*/M* theory and de Sitter supergravity
We construct consistent non-linear Kaluza Klein reduction ansatze for a
subset of fields arising from the reduction of IIB* and M* theory on dS_5 x H^5
and dS_4 x AdS_7, respectively. These reductions yield four and
five-dimensional de Sitter supergravities, albeit with wrong sign kinetic
terms. We also demonstrate that the ansatze may be used to lift multi-centered
de Sitter black hole solutions to ten and eleven dimensions. The lifted dS_5
black holes correspond to rotating E4-branes of IIB* theory.Comment: 27 pages, late
Black Holes in Supergravity and String Theory
We give an elementary introduction to black holes in supergravity and string
theory. The focus is on BPS solutions in four- and higher-dimensional
supergravity and string theory. Basic ideas and techniques are explained in
detail, including exercises with solutions.Comment: 64 pages, based on lectures given at the school of the TMR network
'Quantum aspects of gauge theories, supersymmetry and unification' in Torino,
January 26 - February 2, 2000. To be published in Class. Quant. Grav. (Some
typos corrected, two references added.
Supersymmetry of Black Strings in D=5 Gauged Supergravities
Supersymmetry of five dimensional string solutions is examined in the context
of gauged D=5, N=2 supergravity coupled to abelian vector multiplets. We find
magnetic black strings preserving one quarter of supersymmetry and approaching
the half-supersymmetric product space AdS_3\times H^2 near the event horizon.
The solutions thus exhibit the phenomenon of supersymmetry enhancement near the
horizon, like in the cases of ungauged supergravity theories, where the near
horizon limit is fully supersymmetric. Finally, product space compactifications
are studied in detail, and it is shown that only for negative curvature
(hyperbolic) internal spaces, some amount of supersymmetry can be preserved.
Among other solutions, we find that the extremal rotating BTZ black hole
tensored by H^2 preserves one quarter of supersymmetry.Comment: 19 pages, LaTeX, no figures, published versio
HKT Geometry and Fake Five Dimensional Supergravity
Recent results on the relation between hyper-Kahler geometry with torsion and
solutions admitting Killing spinors in minimal de sitter supergravity are
extended to more general supergravity models with vector multiplets.Comment: 14 pages, latex. Minor typos corrected, references adde
Solutions of Minimal Four Dimensional de Sitter Supergravity
Pseudo-supersymmetric solutions of minimal , de Sitter
supergravity are classified using spinorial geometry techniques. We find three
classes of solutions. The first class of solution consists of geometries which
are fibrations over a 3-dimensional manifold equipped with a Gauduchon-Tod
structure. The second class of solution is the cosmological Majumdar-Papapetrou
solution of Kastor and Traschen, and the third corresponds to gravitational
waves propagating in the Nariai cosmology.Comment: 17 Pages. Minor correction to section 4; equation (4.21) corrected
and (old) equation (4.26) deleted; the final result is unchange
From de Sitter to de Sitter
We obtain D=6, N=(1,1) de Sitter supergravity from a hyperbolic reduction of
the massive type IIA* theory. We construct a smooth cosmological solution in
which the co-moving time runs from an infinite past, which is dS_4\times S^2,
to an infinite future, which is a dS_6-type spacetime with the boundary
R^3\times S^2. This provides an effective four-dimensional cosmological model
with two compact extra dimensions forming an S^2. Interestingly enough,
although the solution is time-dependent, it arises from a first-order system
via a superpotential construction. We lift the solutions back to D=10, and in
particular obtain two smooth embeddings of dS_4 in massive type IIA*, with the
internal space being either H^4\times S^2 or an H^4 bundle over S^2. We also
obtain the analogous D=5 and D=4 solutions. We show that there exist
cosmological solutions that describe an expanding universe with the expansion
rate significantly larger in the past than in the future.Comment: Latex three times, 22 pages, references adde
Anti-de Sitter/CFT Correspondence in Three-Dimensional Supergravity
Anti-de Sitter supergravity models are considered in three dimensions.
Precise asymptotic conditions involving a chiral projection are given on the
Rarita-Schwinger fields. Together with the known boundary conditions on the
bosonic fields, these ensure that the asymptotic symmetry algebra is the
superconformal algebra. The classical central charge is computed and found to
be equal to the one of pure gravity. It is also indicated that the asymptotic
degrees of freedom are described by 2D "induced supergravity" and that the
boundary conditions "transmute" the non-vanishing components of the WZW
supercurrent into the supercharges.Comment: Additional remarks in the extended case, added references, and small
misprints corrected. To appear in Phys. Rev. D. Latex, 19 pages, no figure
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