192 research outputs found
N=31, D=11
We show that eleven-dimensional supergravity backgrounds with thirty one
supersymmetries, N=31, admit an additional Killing spinor and so they are
locally isometric to maximally supersymmetric ones. This rules out the
existence of simply connected eleven-dimensional supergravity preons. We also
show that N=15 solutions of type I supergravities are locally isometric to
Minkowski spacetime.Comment: 17 page
The holonomy of the supercovariant connection and Killing spinors
We show that the holonomy of the supercovariant connection for M-theory
backgrounds with Killing spinors reduces to a subgroup of SL(32-N,\bR)\st
(\oplus^N \bR^{32-N}). We use this to give the necessary and sufficient
conditions for a background to admit Killing spinors. We show that there is
no topological obstruction for the existence of up to 22 Killing spinors in
eleven-dimensional spacetime. We investigate the symmetry superalgebras of
supersymmetric backgrounds and find that their structure constants are
determined by an antisymmetric matrix. The Lie subalgebra of bosonic generators
is related to a real form of a symplectic group. We show that there is a
one-one correspondence between certain bases of the Cartan subalgebra of
sl(32, \bR) and supersymmetric planar probe M-brane configurations. A
supersymmetric probe configuration can involve up to 31 linearly independent
planar branes and preserves one supersymmetry. The space of supersymmetric
planar probe M-brane configurations is preserved by an SO(32,\bR) subgroup of
SL(32, \bR).Comment: 27 pages, a key reference was added. v3: minor change
The Geometry of D=11 Null Killing Spinors
We determine the necessary and sufficient conditions on the metric and the
four-form for the most general bosonic supersymmetric configurations of D=11
supergravity which admit a null Killing spinor i.e. a Killing spinor which can
be used to construct a null Killing vector. This class covers all
supersymmetric time-dependent configurations and completes the classification
of the most general supersymmetric configurations initiated in hep-th/0212008.Comment: 30 pages, typos corrected, reference added, new solution included in
section 5.1; uses JHEP3.cl
Uniqueness of Five-Dimensional Supersymmetric Black Holes
A classification of supersymmetric solutions of five dimensional ungauged
supergravity coupled to arbitrary many abelian vector multiplets is used to
prove a uniqueness theorem for asymptotically flat supersymmetric black holes
with regular horizons. It is shown that the near-horizon geometries of
solutions for which the scalars and gauge field strengths are sufficiently
regular on the horizon are flat space, AdS_3 x S^2, or the near-horizon BMPV
solution. Furthermore, the only black hole which has the near-horizon BMPV
geometry for its near-horizon geometry is the solution found by Chamseddine and
Sabra.Comment: 15 pages, uses JHEP3.cls. Revised to match published version;
reference added, minor alterations to section
Test de Zohlen y su relación con el ángulo Q en población sin dolor patelofemoral
ResumenObjetivoDeterminar qué porcentaje de una población sin dolor anterior de rodilla tiene un test de Zohlen positivo, además determinar el ángulo Q de esta población y buscar si existe alguna relación entre la positividad del test de Zohlen y alteraciones en el ángulo Q.Material y métodoEstudio descriptivo-prospectivo observacional. Aplicación del test de Zohlen y medición del ángulo Q. La población se dividió en 2 grupos: test de Zohlen positivo y test de Zohlen negativo. Cuantificación y comparación de medias del ángulo Q en los dos grupos.Resultados90 sujetos evaluados, promedio de edad 20,18 años (18-40). Veinte sujetos (22,2%) con test de Zohlen positivo. Ángulo Q promedio en los sujetos con test de Zohlen negativo: 14,95°; ángulo Q promedio en los sujetos con test de Zohlen positivo: 16,9° (p < 0,05).Ángulo Q promedio en hombres con test de Zohlen negativo13,4°; ángulo Q promedio en hombres con test de Zohlen positivo: 16° (p < 0,05). Ángulo Q promedio en mujeres con test de Zohlen negativo: 16,5°; ángulo Q promedio en mujeres con test de Zohlen positivo: 18°, sin diferencias estadísticamente significativas entre ambos grupos.ConclusionesEl test de Zohlen tiene una correlación positiva con el ángulo Q en sujetos de sexo masculino. Dada la correlación entre un ángulo Q alterado y la presencia de dolor anterior de rodilla, en los pacientes que presentan un test de Zohlen positivo sin haber consultado por dolor anterior de rodilla, la prevención primaria de dolor anterior de rodilla puede ser de utilidad.AbstractObjectiveTo determine the percentage of a population without anterior knee pain with a positive Zohlen test, and also to determine the Q angle of this population and to determine if there is any relationship between the Zohlen test and Q angle anomalies.MethodsA prospective observational study was conducted in which Zohleńs test was applied and the Q angle was measured. The population was divided into 2 groups: Zohleńs positive and Zohleńs negative. Q angle was compared in the 2 groups.ResultsThe study included 90 subjects, with a mean age 20.18 years (18-40), of whom 20 subjects (22.2%) had positive Zohleńs test. The mean Q angle in subjects with negative Zohleńs test was 14.95°, and the mean Q angle in subjects with positive Zohleńs test was 16,9° (p<.05). The mean Q angle in men with negative Zohleńs test was 13.4°, and the mean Q angle in men with positive Zohleńs test was 16° (p < .05). The mean Q angle in women with negative Zohleńs test was 16.5°, with a mean Q angle of 18° in women with positive Zohleńs test, with no statistically significant differences found between groups.ConclusionsZohleńs test has a positive correlation with the Q angle in male subjects. Given the correlation between the Q angle and the presence of anterior knee pain in patients who have a positive test without symptoms, primary prevention of anterior knee pain can be achieved
The Geometry of D=11 Killing Spinors
We propose a way to classify all supersymmetric configurations of D=11
supergravity using the G-structures defined by the Killing spinors. We show
that the most general bosonic geometries admitting a Killing spinor have at
least a local SU(5) or an (Spin(7)\ltimes R^8)x R structure, depending on
whether the Killing vector constructed from the Killing spinor is timelike or
null, respectively. In the former case we determine what kind of local SU(5)
structure is present and show that almost all of the form of the geometry is
determined by the structure. We also deduce what further conditions must be
imposed in order that the equations of motion are satisfied. We illustrate the
formalism with some known solutions and also present some new solutions
including a rotating generalisation of the resolved membrane solutions and
generalisations of the recently constructed D=11 Godel solution.Comment: 36 pages. Typos corrected and discussion on G-structures improved.
Final version to appear in JHE
Marginal Deformations of Field Theories with AdS_4 Duals
We generate new AdS_4 solutions of D=11 supergravity starting from AdS_4 x
X_7 solutions where X_7 has U(1)^3 isometry. We consider examples where X_7 is
weak G_2, Sasaki-Einstein or tri-Sasakian, corresponding to d=3 SCFTs with
N=1,2 or 3 supersymmetry, respectively, and where the deformed solutions
preserve N=1,2 or 1 supersymmetry, respectively. For the special cases when X_7
is M(3,2), Q(1,1,1) or N(1,1)_I we identify the exactly marginal deformation in
the dual field theory. We also show that the volume of supersymmetric 5-cycles
of N(1,1)_I agrees with the conformal dimension predicted by the baryons of the
dual field theory.Comment: 28 pages, 2 figures; v2. typos correcte
Fast k-NN classifier for documents based on a graph structure
In this paper, a fast k nearest neighbors (k-NN) classifier for documents is presented. Documents are usually represented in a high-dimensional feature space, where terms appeared on it are treated as features and the weight of each term reflects its importance in the document. There are many approaches to find the vicinity of an object, but their performance drastically decreases as the number of dimensions grows. This problem prevents its application for documents. The proposed method is based on a graph index structure with a fast search algorithm. It’s high selectivity permits to obtain a similar classification quality than exhaustive classifier, with a few number of computed distances. Our experimental results show that it is feasible the use of the proposed method in problems of very high dimensionality, such as Text Mining
Kappa symmetry, generalized calibrations and spinorial geometry
We extend the spinorial geometry techniques developed for the solution of
supergravity Killing spinor equations to the kappa symmetry condition for
supersymmetric brane probe configurations in any supergravity background. In
particular, we construct the linear systems associated with the kappa symmetry
projector of M- and type II branes acting on any Killing spinor. As an example,
we show that static supersymmetric M2-brane configurations which admit a
Killing spinor representing the SU(5) orbit of are generalized
almost hermitian calibrations and the embedding map is pseudo-holomorphic. We
also present a bound for the Euclidean action of M- and type II branes embedded
in a supersymmetric background with non-vanishing fluxes. This leads to an
extension of the definition of generalized calibrations which allows for the
presence of non-trivial Born-Infeld type of fields in the brane actions.Comment: 9 pages, latex, references added and minor change
A Brane Teaser
In this note we study the puzzle posed by two M5-branes intersecting on a
string (or equivalently, a single M5-brane wrapping a holomorphic four-cycle in
C^4). It has been known for a while that this system is different from all
other configurations built using self-intersecting M-branes; in particular the
corresponding supergravity solution exhibits various curious features which
have remained unexplained. We propose that the resolution to these puzzles lies
in the existence of a non-zero two-form on the M5-brane world-volume.Comment: 21 pages. References adde
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