79 research outputs found
Supersymmetric Intersecting D6-Branes and Fluxes in Massive Type IIA String Theory
We study N=1 supersymmetric four-dimensional solutions of massive Type IIA supergravity with intersecting D6-branes in the presence NS-NS three-form fluxes. We derive N=1 supersymmetry conditions for the D6-brane and flux configurations in an internal manifold X6 and derive the intrinsic torsion (or SU(3)-structure) related to the fluxes. In the absence of fluxes, N=1 supersymmetry implies that D6-branes wrap supersymmetric three-cycles of X6 that intersect at angles of SU(3) rotations and the geometry is deformed by SU(3)-structures. The presence of fluxes breaks the SU(3) structures to SU(2) and the D6-branes intersect at angles of SU(2) rotations; non-zero mass parameter corresponds to D8-branes which are orthogonal to the common cycle of all D6-branes. The anomaly inflow indicates that the gauge theory on intersecting (massive) D6-branes is not chiral
Domain Wall World(s)
Gravitational properties of domain walls in fundamental theory and their
implications for the trapping of gravity are reviewed. In particular, the
difficulties to embed gravity trapping configurations within gauged
supergravity is reviewed and the status of the domain walls obtained via the
breathing mode of sphere reduced Type IIB supergravity is presented.Comment: 11 pages, Based on talk given at Strings 2000 Minor corrections,
references adde
Time-dependent backgrounds from supergravity with gauged non-compact R-symmetry
We obtain a general class of time-dependent, asymptotically de Sitter backgrounds which solve the first order bosonic equations that extremize the action for supergravity with gauged non-compact R-symmetry. These backgrounds correspond only to neutral fields with the correct sign of kinetic energy. Within N=2 five-dimensional supergravity with vector-superfields we provide examples of multi-centered charged black holes in asymptotic de Sitter space, whose spatial part is given by a timedependent hyper-Kähler space. Reducing these backgrounds to four dimensions yields asymptotically de Sitter multi-centered charged black hole backgrounds and we show that they are related to an instanton configuration by a massive T-duality over time. Within N=2 gauged supergravity in four (and five)-dimensions with hyper-multiplets there could also be neutral cosmological backgrounds that are regular and correspond to the different de Sitter spaces at early and late times
Time-dependent backgrounds from supergravity with gauged non-compact R-symmetry
We obtain a general class of time-dependent, asymptotically de Sitter
backgrounds which solve the first order bosonic equations that extremize the
action for supergravity with gauged non-compact -symmetry. These backgrounds
correspond only to neutral fields with the correct sign of kinetic energy.
Within N=2 five-dimensional supergravity with vector-superfields we provide
examples of multi-centered charged black holes in asymptotic de Sitter space,
whose spatial part is given by a time-dependent hyper-K\"ahler space. Reducing
these backgrounds to four dimensions yields asymptotically de Sitter
multi-centered charged black hole backgrounds and we show that they are related
to an instanton configuration by a massive T-duality over time. Within N=2
gauged supergravity in four (and five)-dimensions with hyper-multiplets there
could also be neutral cosmological backgrounds that are regular and correspond
to the different de Sitter spaces at early and late times.Comment: 28 pages, Latex; minor changes and add reference
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
Fluxes in M-theory on 7-manifolds and G structures
We consider warp compactifications of M-theory on 7-manifolds in the presence
of 4-form fluxes and investigate the constraints imposed by supersymmetry. As
long as the 7-manifold supports only one Killing spinor we infer from the
Killing spinor equations that non-trivial 4-form fluxes will necessarily curve
the external 4-dimensional space. On the other hand, if the 7-manifold has at
least two Killing spinors, there is a non-trivial Killing vector yielding a
reduction of the 7-manifold to a 6-manifold and we confirm that 4-form fluxes
can be incorporated if one includes non-trivial SU(3) structures.Comment: 13 pages, Latex; minor changes & add reference
Black hole entropy reveals a 12th "dimension"
The Beckenstein-Hawking black hole entropy in string theory and its
extensions, as expressed in terms of charges that correspond to central
extensions of the supersymmetry algebra, has more symmetries than U-duality. It
is invariant under transformations of the charges, involving a 12th (or 13th)
``dimension''. This is an indication that the secret theory behind string
theory has a superalgebra involving Lorentz non-scalar extensions (that are not
strictly central), as suggested in S-theory, and which could be hidden in M- or
F- theories. It is suggested that the idea of spacetime is broader than usual,
and that a larger ``spacetime" is partially present in black holes.Comment: Latex, 20 pages, minor formatting correction
BPS Domain Wall Junctions in Infinitely Large Extra Dimensions
We consider models of scalar fields coupled to gravity which are
higher-dimensional generalizations of four dimensional supergravity. We use
these models to describe domain wall junctions in an anti-de Sitter background.
We derive Bogomolnyi equations for the scalar fields from which the walls are
constructed and for the metric. From these equations a BPS-like formula for the
junction energy can be derived. We demonstrate that such junctions localize
gravity in the presence of more than one uncompactified extra dimension.Comment: 17 pages, uses RevTeX, new references adde
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