833 research outputs found
Index theory and dynamical symmetry enhancement of M-horizons
We show that near-horizon geometries of 11-dimensional supergravity preserve
an even number of supersymmetries. The proof follows from Lichnerowicz type
theorems for two horizon Dirac operators, the field equations and Bianchi
identities, and the vanishing of the index of a Dirac operator on the
9-dimensional horizon sections. As a consequence of this, we also prove that
all M-horizons with non-vanishing fluxes admit a sl(2,R) subalgebra of
symmetries.Comment: Minor typos corrected. 22 pages, latex. Repeats equations and
descriptions from arXiv:1207.708
On supersymmetric AdS6 solutions in 10 and 11 dimensions
We prove a non-existence theorem for smooth, supersymmetric, warped AdS6
solutions with connected, compact without boundary internal space in D=11 and
(massive) IIA supergravities. In IIB supergravity we show that if such AdS6
solutions exist, then the NSNS and RR 3-form fluxes must be linearly
independent and certain spinor bi-linears must be appropriately restricted.
Moreover we demonstrate that the internal space admits an so(3) action which
leaves all the fields invariant and for smooth solutions the principal orbits
must have co-dimension two. We also describe the topology and geometry of
internal spaces that admit such a so(3) action and show that there are no
solutions for which the internal space has topology F * S^2, where F is an
oriented surface.Comment: 26 pages, late
Gravitational Instantons and Euclidean Supersymmetry
Supersymmetric instanton solutions in four dimensional Euclidean ungauged
Einstein-Maxwell theory are analysed and classified according to the fraction
of supersymmetry they preserve, using spinorial geometry techniques.Comment: 10 pages, late
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
Vanishing Preons in the Fifth Dimension
We examine supersymmetric solutions of N=2, D=5 gauged supergravity coupled
to an arbitrary number of abelian vector multiplets using the spinorial
geometry method. By making use of methods developed in hep-th/0606049 to
analyse preons in type IIB supergravity, we show that there are no solutions
preserving exactly 3/4 of the supersymmetry.Comment: 19 pages, latex. Reference added, and further modification to the
introductio
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