5,893 research outputs found

    Common subbundles and intersections of divisors

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    Let V_0 and V_1 be complex vector bundles over a space X. We use the theory of divisors on formal groups to give obstructions in generalised cohomology that vanish when V_0 and V_1 can be embedded in a bundle U in such a way that V_0\cap V_1 has dimension at least k everywhere. We study various algebraic universal examples related to this question, and show that they arise from the generalised cohomology of corresponding topological universal examples. This extends and reinterprets earlier work on degeneracy classes in ordinary cohomology or intersection theory.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol2/agt-2-42.abs.htm

    Judicially Compelled Disclosure of Researchers’ Data: A Judge’s View

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    Crabb looks at the approach one court has established to balance the demands of the legal system with the legitimate concerns of researchers

    Obstruction theory on 8-manifolds

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    This note gives a uniform, self-contained, and fairly direct approach to a variety of obstruction-theoretic problems on 8-manifolds. We give necessary and sufficient cohomological critera for the existence of almost complex and almost quaternionic structures on the tangent bundle and for the reduction of the structure group to U(3) by the homomorphism U(3) --> O(8) given by the Lie algebra representation of PU(3).Comment: 19 page

    High Rate Neutrino Detectors for Neutrino Factories

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    Three types of high rate neutrino detectors for neutrino interaction physics at neutrino factories are discussed. High performance general-purpose detectors might collect event samples on the order of a billion events or more. This could greatly improve on existing analyses of neutrino interactions and also lead to new and important analysis topics including, for example, precise determinations of the CKM matrix elements |Vub| and |Vcb|. The potential of such general purpose detectors is illustrated with reference to a detector, presented previously in reference hep-ex/9907033, that is structured around a novel and compact vertexing and tracking neutrino target comprising a stack of CCD pixel devices. Design ideas and prospects are also discussed for two types of specialized detectors: (i) polarized targets filled with polarized solid protium-deuterium (HD), for unique and powerful studies of the nucleon's spin structure, and (ii) Fully active liquid tracking targets with masses of several tonnes for precise determinations of the weak mixing angle, from the total cross-section for neutrino-electron scattering. All three detector types pose severe technical challenges but their utilization could add significantly to the physics motivation for neutrino factories.Comment: 12 pages, 1 figure. Submitted to Proc. ICFA/ECFA Workshop "Neutrino Factories based on Muon Storage Rings" (nuFACT'99), Lyon, France, 5--9 July, 199

    The extremal algebra on two hermitians with square 1

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    Let Ea(u,v) be the extremal algebra determined by two hermitians u and v with u2 = v2 = 1. We show that: Ea(u,v) = {f=gu:f,g ε C(T)}, where T is the unit circle; Ea(u,v) is C*-equivelant to C*(G), where G is the infinite dihedral group; most of the hermitian elements k od Ea(u,v) have the property that kn is hermitian for all odd n but for no even n; any two hermitian words in G generate an isometric copy of Ea(u,v) in Ea(u,v)
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