40,915 research outputs found

    Nuclear Multifragmentation Critical Exponents

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    We show that the critical exponents of nuclear multi-fragmentation have not been determined conclusively yet.Comment: 3 pages, LaTeX, one postscript figure appended, sub. to Phys.Rev.Lett. as a commen

    Present and Future in Semileptonic B Decays

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    In this talk I review the status of our ability to extract the CKM matrix elements |Vub| and |Vcb| from semileptonic decays. I will review both exclusive and inclusive methods and put a strong emphasis on how to ensure keeping the extractions model independent.Comment: 10 pages, Invited plenary talk presented at 9th International Symposium on Heavy Flavor Physics, Caltech, Sep. 10-13, 200

    Phase Transitions in a Two-Component Site-Bond Percolation Model

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    A method to treat a N-component percolation model as effective one component model is presented by introducing a scaled control variable p+p_{+}. In Monte Carlo simulations on 16316^{3}, 32332^{3}, 64364^{3} and 1283128^{3} simple cubic lattices the percolation threshold in terms of p+p_{+} is determined for N=2. Phase transitions are reported in two limits for the bond existence probabilities p=p_{=} and pp_{\neq}. In the same limits, empirical formulas for the percolation threshold p+cp_{+}^{c} as function of one component-concentration, fbf_{b}, are proposed. In the limit p==0p_{=} = 0 a new site percolation threshold, fbc0.145f_{b}^{c} \simeq 0.145, is reported.Comment: RevTeX, 5 pages, 5 eps-figure

    Uniqueness of the Fisher-Rao metric on the space of smooth densities

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    MB was supported by ‘Fonds zur F¨orderung der wissenschaftlichen Forschung, Projekt P 24625’

    Reparameterization Invariance for Collinear Operators

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    We discuss restrictions on operators in the soft-collinear effective theory (SCET) which follow from the ambiguity in the decomposition of collinear momenta and the freedom in the choice of light-like basis vectors nn and nˉ\bar n. Invariance of SCET under small changes in nn and/or nˉ\bar n implies a symmetry of the effective theory that constrains the form of allowed operators with collinear fields. The restrictions occur at a given order in the power counting as well as between different orders. As an example, we present the complete set of higher order operators that are related to the collinear quark kinetic term.Comment: 11 page

    Invariant Operators in Collinear Effective Theory

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    We consider processes which produce final state hadrons whose energy is much greater than their mass. In this limit interactions involving collinear fermions and gluons are constrained by a symmetry, and we give a general set of rules for constructing leading and subleading invariant operators. Wilson coefficients C(mu,P) are functions of a label operator P, and do not commute with collinear fields. The symmetry is used to reproduce a two-loop result for factorization in B -> D pi in a simple way.Comment: 11 pages, 2 figs, journal versio

    "Don't panic": a primer on airline deregulation

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    A summary of the theory behind airline deregulation, and a look at the future evolution of the airline industry as it adapts to its new environment.Airlines ; Industrial policy

    A beginner's guide to the U.S. payments system

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    A description of the U.S. payments system, outlining its evolution and examining some of the areas where improvements are needed.Payment systems
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