1,071 research outputs found

    Deformations of generalized calibrations and compact non-Kahler manifolds with vanishing first Chern class

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    We investigate the deformation theory of a class of generalized calibrations in Riemannian manifolds for which the tangent bundle has reduced structure group U(n), SU(n), G_2 and Spin(7). For this we use the property of the associated calibration form to be parallel with respect to a metric connection which may have non-vanishing torsion. In all these cases, we find that if there is a moduli space, then it is finite dimensional. We present various examples of generalized calibrations that include almost hermitian manifolds with structure group U(n) or SU(n), nearly parallel G_2 manifolds and group manifolds. We find that some Hopf fibrations are deformation families of generalized calibrations. In addition, we give sufficient conditions for a hermitian manifold (M,g,J) to admit Chern and Bismut connections with holonomy contained in SU(n). In particular we show that any connected sum of k3k \geq 3 copies of S3×S3S^3 \times S^3 admits a hermitian structure for which the restricted holonomy of a Bismut connection is contained in SU(3).Comment: 43 pages, Latex, typos corrected, reference added in section

    Geometry and supersymmetry of heterotic warped flux AdS backgrounds

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    We classify the geometries of the most general warped, flux AdS backgrounds of heterotic supergravity up to two loop order in sigma model perturbation theory. We show under some mild assumptions that there are no AdSnAdS_n backgrounds with n3n\not=3. Moreover the warp factor of AdS3_3 backgrounds is constant, the geometry is a product AdS3×M7AdS_3\times M^7 and such solutions preserve, 2, 4, 6 and 8 supersymmetries. The geometry of M7M^7 has been specified in all cases. For 2 supersymmetries, it has been found that M7M^7 admits a suitably restricted G2G_2 structure. For 4 supersymmetries, M7M^7 has an SU(3)SU(3) structure and can be described locally as a circle fibration over a 6-dimensional KT manifold. For 6 and 8 supersymmetries, M7M^7 has an SU(2)SU(2) structure and can be described locally as a S3S^3 fibration over a 4-dimensional manifold which either has an anti-self dual Weyl tensor or a hyper-K\"ahler structure, respectively. We also demonstrate a new Lichnerowicz type theorem in the presence of α\alpha' corrections.Comment: 34 pages. Reference adde

    All Killing Superalgebras for Warped AdS Backgrounds

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    We present all the symmetry superalgebras g\mathfrak{g} of all warped AdSk×wMdk_k\times_w M^{d-k}, k>2k>2, flux backgrounds in d=10,11d=10, 11 dimensions preserving any number of supersymmetries. First we give the conditions for g\mathfrak{g} to decompose into a direct sum of the isometry algebra of AdSk_k and that of the internal space MdkM^{d-k}. Assuming this decomposition, we identify all symmetry superalgebras of AdS3_3 backgrounds by showing that the isometry groups of internal spaces act transitively on spheres. We demonstrate that in type II and d=11d=11 theories the AdS3_3 symmetry superalgebras may not be simple and also present all symmetry superalgebras of heterotic AdS3_3 backgrounds. Furthermore, we explicitly give the symmetry superalgebras of AdSk_k, k>3k>3, backgrounds and prove that they are all classical.Comment: 41 pages, late

    HKT Geometry and Fake Five Dimensional Supergravity

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    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

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    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

    Maximally Minimal Preons in Four Dimensions

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    Killing spinors of N=2, D=4 supergravity are examined using the spinorial geometry method, in which spinors are written as differential forms. By making use of methods developed in hep-th/0606049 to analyze preons in type IIB supergravity, we show that there are no simply connected solutions preserving exactly 3/4 of the supersymmetry.Comment: 18 pages. References added, comments added discussing the possibility of discrete quotients of AdS(4) preserving 3/4 supersymmetry

    Calibrated Entanglement Entropy

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    The Ryu-Takayanagi prescription reduces the problem of calculating entanglement entropy in CFTs to the determination of minimal surfaces in a dual anti-de Sitter geometry. For 3D gravity theories and BTZ black holes, we identify the minimal surfaces as special Lagrangian cycles calibrated by the real part of the holomorphic one-form of a spacelike hypersurface. We show that (generalised) calibrations provide a unified way to determine holographic entanglement entropy from minimal surfaces, which is applicable to warped AdS3_3 geometries. We briefly discuss generalisations to higher dimensions.Comment: v1 22 pages, 1 figure; v2 appendix improved and moved into the body to show the application of calibrations to find minimal surfaces in warped AdS, matches published versio

    Do supersymmetric anti-de Sitter black rings exist?

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    We determine the most general near-horizon geometry of a supersymmetric, asymptotically anti-de Sitter, black hole solution of five-dimensional minimal gauged supergravity that admits two rotational symmetries. The near-horizon geometry is that of the supersymmetric, topologically spherical, black hole solution of Chong et al. This proves that regular supersymmetric anti-de Sitter black rings with two rotational symmetries do not exist in minimal supergravity. However, we do find a solution corresponding to the near-horizon geometry of a supersymmetric black ring held in equilibrium by a conical singularity, which suggests that nonsupersymmetric anti-de Sitter black rings may exist but cannot be "balanced" in the supersymmetric limit.Comment: Latex, 18 pages, 1 figure. v2: minor change

    Mapping the G-structures and supersymmetric vacua of five-dimensional N=4 supergravity

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    We classify the supersymmetric vacua of N=4, d=5 supergravity in terms of G-structures. We identify three classes of solutions: with R^3, SU(2) and generic SO(4) structure. Using the Killing spinor equations, we fully characterize the first two classes and partially solve the latter. With the N=4 graviton multiplet decomposed in terms of N=2 multiplets: the graviton, vector and gravitino multiplets, we obtain new supersymmetric solutions corresponding to turning on fields in the gravitino multiplet. These vacua are described in terms of an SO(5) vector sigma-model coupled with gravity, in three or four dimensions. A new feature of these N=4 vacua, which is not seen from an N=2 point of view, is the possibility for preserving more exotic fractions of supersymmetry. We give a few concrete examples of these new supersymmetric (albeit singular) solutions. Additionally, we show how by truncating the N=4, d=5 set of fields to minimal supergravity coupled with one vector multiplet we recover the known two-charge solutions.Comment: 31 pages, late

    All null supersymmetric backgrounds of N=2, D=4 gauged supergravity coupled to abelian vector multiplets

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    The lightlike supersymmetric solutions of N=2, D=4 gauged supergravity coupled to an arbitrary number of abelian vector multiplets are classified using spinorial geometry techniques. The solutions fall into two classes, depending on whether the Killing spinor is constant or not. In both cases, we give explicit examples of supersymmetric backgrounds. Among these BPS solutions, which preserve one quarter of the supersymmetry, there are gravitational waves propagating on domain walls or on bubbles of nothing that asymptote to AdS_4. Furthermore, we obtain the additional constraints obeyed by half-supersymmetric vacua. These are divided into four categories, that include bubbles of nothing which are asymptotically AdS_4, pp-waves on domain walls, AdS_3 x R, and spacetimes conformal to AdS_3 times an interval.Comment: 55 pages, uses JHEP3.cls. v2: Minor errors corrected, small changes in introductio
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