1,673 research outputs found
Horizons in de-Sitter Supergravity
We classify all pseudo-supersymmetric extremal near-horizon geometries in
minimal five-dimensional de-Sitter supergravity. It is shown that the only such
near-horizon geometry is the near-horizon geometry of the de-Sitter BMPV
solution, and hence there are no regular extremal pseudo-supersymmetric
asymptotically de-Sitter black rings.Comment: 26 pages, latex. Minor typos in equations (4.16) and (6.12) correcte
Heterotic horizons, Monge-Ampere equation and del Pezzo surfaces
Heterotic horizons preserving 4 supersymmetries have sections which are T^2
fibrations over 6-dimensional conformally balanced Hermitian manifolds. We give
new examples of horizons with sections S^3 X S^3 X T^2 and SU(3). We then
examine the heterotic horizons which are T^4 fibrations over a Kahler
4-dimensional manifold. We prove that the solutions depend on 6 functions which
are determined by a non-linear differential system of 6 equations that include
the Monge-Ampere equation. We show that this system has an explicit solution
for the Kahler manifold S^2 X S^2. We also demonstrate that there is an
associated cohomological system which has solutions on del Pezzo surfaces. We
raise the question of whether for every solution of the cohomological problem
there is a solution of the differential system, and so a new heterotic horizon.
The horizon sections have topologies which include ((k-1) S^2 X S^4 # k (S^3 X
S^3)) X T^2$ indicating the existence of exotic black holes. We also find an
example of a horizon section which gives rise to two different near horizon
geometries.Comment: 33 pages, latex. Reference adde
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
Index theory and dynamical symmetry enhancement near IIB horizons
We show that the number of supersymmetries of IIB black hole horizons is N=2
N_- + 2 index(D_\lambda), where index(D_\lambda) is the index of the Dirac
operator twisted with the line bundle \lambda^{1/2} of IIB scalars, and N_- is
the dimension of the kernel of a horizon Dirac operator which depends on IIB
fluxes. Therefore, all IIB horizons preserve an even number of supersymmetries.
In addition if the horizons have non-trivial fluxes and N_- is nonzero, then
index(D_\lambda) is non-negative, and the horizons admit an sl(2,R) symmetry
subalgebra. This provides evidence that all such horizons have an AdS/CFT dual.
Furthermore if the orbits of sl(2,R) are two-dimensional, the IIB horizons are
warped products AdS_2 X S.Comment: 37 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
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