170,841 research outputs found

    Comment on "Superinstantons and the Reliability of Perturbation Theory in Non-Abelian Models"

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    In a recent letter (hep-lat/9311019) A. Patrascioiu and E. Seiler argued that when taking into account "superinstantons configurations" the perturbative expansion and the beta-function of the two-dimensional non-linear sigma-model are modified at two loops order. I point out that: (1) perturbation theory in a superinstanton background is infra-red singular beyond three loops; (2) the new infra-red singular terms, which change the two loop terms, come from singular operators - describing superinstanton insertions - in the OPE; (3) taking into account these operators, the beta-function is not modified. Therefore the results of Patrascioiu and Seiler do not contradict perturbation theory.Comment: 1 page, REVTeX, no figure

    Foreword

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    The Consumer’s Stake in the Finance Company Code Controversy

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    The duality between time and frequency domain methods for linear systems is well known. It plays a crucial role for example in control systems design, and the domains are thought of complementing rather than competing. Quite recently, the full interplay and duality between the two domains have been clear also in system identification applications. In this contribution, this duality is discussed. The emphasis is on how it can be used to create a software environment for linear system identification that is as transparent as possible with respect to the data domains

    The Changing Choice-of-Law Process and the Federal Courts

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    As Time Goes by ???: Revisiting Fundamentals

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