2,146 research outputs found

    Singularities of equidistants and global centre symmetry sets of Lagrangian submanifolds

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    We define the Global Centre Symmetry set (GCS) of a smooth closed m-dimensional submanifold M of R^n, n2mn \leq 2m, which is an affinely invariant generalization of the centre of a k-sphere in R^{k+1}. The GCS includes both the centre symmetry set defined by Janeczko and the Wigner caustic defined by Berry. We develop a new method for studying generic singularities of the GCS which is suited to the case when M is lagrangian in R^{2m} with canonical symplectic form. The definition of the GCS, which slightly generalizes one by Giblin and Zakalyukin, is based on the notion of affine equidistants, so, we first study singularities of affine equidistants of Lagrangian submanifolds, classifying all the stable ones. Then, we classify the affine-Lagrangian stable singularities of the GCS of Lagrangian submanifolds and show that, already for smooth closed convex curves in R^2, many singularities of the GCS which are affine stable are not affine-Lagrangian stable.Comment: 26 pages, 2 figure

    Transanal total mesorectal excision with triangle rules: a road map to prevent injuries

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    [Extract] Transanal total mesorectal excision (TaTME) is presented as a promising new surgical technique for the approach to the distal rectum, providing the ability to perform a highquality resection, with technical advantages over the laparoscopic approach. However, the new surgical anatomy of the TaTME resection complicates surgical understanding and increases the risks of inadvertent injuries to important anatomic structures...info:eu-repo/semantics/publishedVersio

    Measurement of jet multiplicity distributions in [Formula: see text] production in pp collisions at [Formula: see text].

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    The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7[Formula: see text] at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0[Formula: see text]. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the [Formula: see text] production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed
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