3,450 research outputs found

    Fibre Bundles and Generalised Dimensional Reduction

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    We study some geometrical and topological aspects of the generalised dimensional reduction of supergravities in D=11 and D=10 dimensions, which give rise to massive theories in lower dimensions. In these reductions, a global symmetry is used in order to allow some of the fields to have a non-trivial dependence on the compactifying coordinates. Global consistency in the internal space imposes topological restrictions on the parameters of the compactification as well as the structure of the space itself. Examples that we consider include the generalised reduction of the type IIA and type IIB theories on a circle, and also the massive ten-dimensional theory obtained by the generalised reduction of D=11 supergravity.Comment: 23 pages, Late

    Massive Three-Dimensional Supergravity From R+R^2 Action in Six Dimensions

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    We obtain a three-parameter family of massive N=1 supergravities in three dimensions from the 3-sphere reduction of an off-shell N=(1,0) six-dimensional Poincare supergravity that includes a curvature squared invariant. The three-dimensional theory contains an off-shell supergravity multiplet and an on-shell scalar matter multiplet. We then generalise this in three dimensions to an eight-parameter family of supergravities. We also find a duality relationship between the six-dimensional theory and the N=(1,0) six-dimensional theory obtained through a T^4 reduction of the heterotic string effective action that includes the higher-order terms associated with the supersymmetrisation of the anomaly-cancelling \tr(R\wedge R) term.Comment: Latex, 32 Pages, an equation is corrected, a few new equations and a number of clarifying remarks are adde

    General Kerr-NUT-AdS Metrics in All Dimensions

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    The Kerr-AdS metric in dimension D has cohomogeneity [D/2]; the metric components depend on the radial coordinate r and [D/2] latitude variables \mu_i that are subject to the constraint \sum_i \mu_i^2=1. We find a coordinate reparameterisation in which the \mu_i variables are replaced by [D/2]-1 unconstrained coordinates y_\alpha, and having the remarkable property that the Kerr-AdS metric becomes diagonal in the coordinate differentials dy_\alpha. The coordinates r and y_\alpha now appear in a very symmetrical way in the metric, leading to an immediate generalisation in which we can introduce [D/2]-1 NUT parameters. We find that (D-5)/2 are non-trivial in odd dimensions, whilst (D-2)/2 are non-trivial in even dimensions. This gives the most general Kerr-NUT-AdS metric in DD dimensions. We find that in all dimensions D\ge4 there exist discrete symmetries that involve inverting a rotation parameter through the AdS radius. These symmetries imply that Kerr-NUT-AdS metrics with over-rotating parameters are equivalent to under-rotating metrics. We also consider the BPS limit of the Kerr-NUT-AdS metrics, and thereby obtain, in odd dimensions and after Euclideanisation, new families of Einstein-Sasaki metrics.Comment: Latex, 24 pages, minor typos correcte

    The double charm decays of BcB_c Meson in the Perturbative QCD Approach

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    We make a systematic investigation on the double charm decays of BcB_c meson, by employing the perturbative QCD approach based on kTk_T factorization. It is found that the non-factorizable emission diagrams are not negligible in these channels. We predict the branching ratios of these BcB_c decays and also the transverse polarization fractions of Bc→D(s)∗+Dˉ∗0,D(s)∗+D∗0B_c\rightarrow D_{(s)}^{*+}\bar D^{*0}, D_{(s)}^{*+}D^{*0} decays, % where V denote the vector D(s)∗D^*_{(s)} meson. We find that the magnitudes of the branching ratios of the decays Bc→DsDˉ0B_c\rightarrow D_s\bar{D}^0 and Bc→DsD0B_c\rightarrow D_sD^0 are very close to each other, which are well suited to extract the Cabibbo-Kobayashi-Maskawa angle γ\gamma through the amplitude relations. In addition, a large transverse polarization contribution that can reach 5050%\sim 60% is predicted in some of the BcB_c meson decay to two vector charmed mesons.Comment: 22 pages, 5 tables, to appear at PRD. arXiv admin note: text overlap with arXiv:1112.125

    Critical and Non-Critical Einstein-Weyl Supergravity

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    We construct N=1 supersymmetrisations of some recently-proposed theories of critical gravity, conformal gravity, and extensions of critical gravity in four dimensions. The total action consists of the sum of three separately off-shell supersymmetric actions containing Einstein gravity, a cosmological term and the square of the Weyl tensor. For generic choices of the coefficients for these terms, the excitations of the resulting theory around an AdS_4 background describe massive spin-2 and massless spin-2 modes coming from the metric; massive spin-1 modes coming from a vector field in the theory; and massless and massive spin-3/2 modes (with two unequal masses) coming from the gravitino. These assemble into a massless and a massive N=1 spin-2 multiplet. In critical supergravity, the coefficients are tuned so that the spin-2 mode in the massive multiplet becomes massless. In the supersymmetrised extensions of critical gravity, the coefficients are chosen so that the massive modes lie in a "window" of lowest energies E_0 such that these ghostlike fields can be truncated by imposing appropriate boundary conditions at infinity, thus leaving just positive-norm massless supergravity modes.Comment: 29 page

    Supersymmetry of the Schrodinger and PP Wave Solutions in Einstein-Weyl Supergravities

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    We obtain the Schrodinger and general pp-wave solutions with or without the massive vector in Einstein-Weyl supergravity. The vector is an auxiliary field in the off-shell supermultiplet and it acquires a kinetic term in the Weyl-squared super invariant. We study the supersymmetry of these solutions and find that turning on the massive vector has a consequence of breaking all the supersymmetry. The Schrodinger and also the pp-wave solutions with the massive vector turned off on the other hand preserve 1/4 of the supersymmetry.Comment: 13 pages, no figur

    Similarity-Based Classification in Partially Labeled Networks

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    We propose a similarity-based method, using the similarity between nodes, to address the problem of classification in partially labeled networks. The basic assumption is that two nodes are more likely to be categorized into the same class if they are more similar. In this paper, we introduce ten similarity indices, including five local ones and five global ones. Empirical results on the co-purchase network of political books show that the similarity-based method can give high accurate classification even when the labeled nodes are sparse which is one of the difficulties in classification. Furthermore, we find that when the target network has many labeled nodes, the local indices can perform as good as those global indices do, while when the data is sparce the global indices perform better. Besides, the similarity-based method can to some extent overcome the unconsistency problem which is another difficulty in classification.Comment: 13 pages,3 figures,1 tabl

    Study of color suppressed modes B0→Dˉ(∗)0η(â€Č)B^0 \to \bar D^{(*)0} \eta^{(\prime)}

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    The color suppressed modes B0→Dˉ(∗)0η(â€Č)B^0 \to \bar D^{(*)0} \eta^{(\prime)} are analyzed in perturbative QCD approach. We find that the dominant contribution is from the non-factorizable diagrams. The branching ratios calculated in our approach for B0→Dˉ(∗)0ηB^0 \to \bar D^{(*)0} \eta agree with current experiments. By neglecting the gluonic contribution, we predict the branching ratios of B0→Dˉ(∗)0ηâ€ČB^0 \to \bar D^{(*)0} \eta' are at the comparable size of B0→Dˉ(∗)0π0B^0 \to \bar D^{(*)0} \pi^0, but smaller than that of B0→Dˉ(∗)0ηB^0 \to \bar D^{(*)0} \eta .Comment: revtex, 5 pages, axodraw.st

    New Einstein-Sasaki Spaces in Five and Higher Dimensions

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    We obtain infinite classes of new Einstein-Sasaki metrics on complete and non-singular manifolds. They arise, after Euclideanisation, from BPS limits of the rotating Kerr-de Sitter black hole metrics. The new Einstein-Sasaki spaces L^{p,q,r} in five dimensions have cohomogeneity 2, and U(1) x U(1) x U(1) isometry group. They are topologically S^2 x S^3. Their AdS/CFT duals will describe quiver theories on the four-dimensional boundary of AdS_5. We also obtain new Einstein-Sasaki spaces of cohomogeneity n in all odd dimensions D=2n+1 \ge 5, with U(1)^{n+1} isometry.Comment: Revtex, 4 pages, metric regularity conditions are further refine
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