28,171 research outputs found

    An exploration of the need for and cost of selected trade facilitation measures in Asia-Pacific in the context of the WTO negotiations

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    This chapter is based on the case studies of Bangladesh, China, India, Indoesnia and NepalTrade facilitation, Bangladesh, China, India, Indonesia, Nepal, Asia Pacific

    An exploration of the need for and cost of selected trade facilitation measures in Asia-Pacific in the context of the WTO negotiations

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    This chapter concludes case studies on trade facilitation measures implementation in Bangladesh, China, Indonesia, India, and Nepaltrade facilitation measures, Bangladesh, China, Indoesnia, India, Nepal

    Review of: Dangerous Places: Health, Safety, and Archaeology (David A. Poirer & Kenneth L. Feder eds.)

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    Review of the book: Dangerous Places: Health, Safety, and Archaeology (David A. Poirier& Kenneth L. Feder eds., Bergin & Garvey, Greenwood Publishing Group, Inc. 2001). Introduction, bibliographic references, index. ISBN0-89789-632-7 [264 pp. $65.00. Cloth, 88 Post Road West, P.O. Box5007, Westport, CT 06881-5007

    Eisenhart lift for higher derivative systems

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    The Eisenhart lift provides an elegant geometric description of a dynamical system of second order in terms of null geodesics of the Brinkmann-type metric. In this work, we attempt to generalize the Eisenhart method so as to encompass higher derivative models. The analysis relies upon Ostrogradsky's Hamiltonian. A consistent geometric description seems feasible only for a particular class of potentials. The scheme is exemplified by the Pais-Uhlenbeck oscillator.Comment: V2: 12 pages, minor improvements, references added; the version to appear in PL

    Galilean Isometries

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    We introduce three nested Lie algebras of infinitesimal `isometries' of a Galilei space-time structure which play the r\^ole of the algebra of Killing vector fields of a relativistic Lorentz space-time. Non trivial extensions of these Lie algebras arise naturally from the consideration of Newton-Cartan-Bargmann automorphisms.Comment: Plain TeX, 8 page

    Polarized Spinoptics and Symplectic Physics

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    We recall the groundwork of spinoptics based on the coadjoint orbits, of given color and spin, of the group of isometries of Euclidean three-space; this model has originally been put forward by Souriau in his treatise "Structure des Syst\'emes Dynamiques", whose manuscript was initially entitled "Physique symplectique". We then set up a model of polarized spinoptics, namely an extension of geometrical optics accounting for elliptically polarized light rays in terms of a certain fibre bundle associated with the bundle of Euclidean frames of a given Riemannian three-manifold. The characteristic foliation of a natural presymplectic two-form introduced on this bundle via the Ansatz of minimal coupling is determined, yielding a set of differential equations governing the trajectory of light, as well as the evolution of polarization in this Riemannian manifold. Those equations, when specialized to the Fermat metric (for a slowly varying refractive index), enable us to recover, and justify, a set of differential equations earlier proposed in the literature, in another context, namely in terms of a semi-classical limit of wave optics. They feature a specific anomalous velocity responsible for the recently observed Spin Hall Effect of Light, namely a tiny spatial deflection of polarized light rays, transversally to the gradient of the refractive index. Our model, constructed from the start on purely geometric grounds, turns out to encode automatically the Berry as well as the Pancharatnam connections that usually appear in the framework of wave optics.Comment: 27 pages, 3 figure

    How to combine diagrammatic logics

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    This paper is a submission to the contest: How to combine logics? at the World Congress and School on Universal Logic III, 2010. We claim that combining "things", whatever these things are, is made easier if these things can be seen as the objects of a category. We define the category of diagrammatic logics, so that categorical constructions can be used for combining diagrammatic logics. As an example, a combination of logics using an opfibration is presented, in order to study computational side-effects due to the evolution of the state during the execution of an imperative program
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