909 research outputs found

    Moyal Representation of the String Field Star Product in the Presence of a B-background

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    In this paper we show that in the presence of an anti-symmetric tensor BB-background, Witten's star algebra for open string fields persists to possess the structure of a direct product of commuting Moyal pairs. The interplay between the noncommutativity due to three-string overlap and that due to the BB-background is our main concern. In each pair of noncommutative directions parallel to the BB-background, the Moyal pairs mix string modes in the two directions and are labeled, in addition to a continuous parameter, by {\it two} discrete values as well. However, the Moyal parameters are BB-dependent only for discrete pairs. We have also demonstrated the large-BB contraction of the star algebra, with one of the discrete Moyal pairs dropping out while the other giving rise to the center-of-mass noncommutative function algebra.Comment: minor notation chang

    The mass gap and vacuum energy of the Gross-Neveu model via the 2PPI expansion

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    We introduce the 2PPI (2-point-particle-irreducible) expansion, which sums bubble graphs to all orders. We prove the renormalizibility of this summation. We use it on the Gross-Neveu model to calculate the mass gap and vacuum energy. After an optimization of the expansion, the final results are qualitatively good.Comment: 14 pages,19 eps figures, revtex

    Renormalization Group Summation and the Free Energy of Hot QCD

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    Using an approach developed in the context of zero-temperature QCD to systematically sum higher order effects whose form is fixed by the renormalization group equation, we sum to all orders the leading log (LL) and next-to-leading log (NLL) contributions to the thermodynamic free energy in hot QCD. While the result varies considerably less with changes in the renormalization scale than does the purely perturbative result, a novel ambiguity arises which reflects the strong scheme dependence of thermal perturbation theory.Comment: 7 pages REVTEX4, 2 figures; v2: typos correcte

    Large N expansion of the 2-matrix model

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    We present a method, based on loop equations, to compute recursively all the terms in the large NN topological expansion of the free energy for the 2-hermitian matrix model. We illustrate the method by computing the first subleading term, i.e. the free energy of a statistical physics model on a discretized torus.Comment: 41 pages, 9 figures eps

    Spiral Multi-component Structure in Pade - Approximant QCD

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    We present a graphical method of analyzing the infra-red fixed point structure of Pade approximant QCD. The analysis shows a spiral multi-component couplant structure as well as an infra-red attractor behavior of PQCD couplant for all flavors 0≤Nf≤160 \le N_{f} \le 16.Comment: 78 pages, 4 tables, 44 graph

    Isotopic composition of fragments in multifragmentation of very large nuclear systems: effects of the chemical equilibrium

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    Studies on the isospin of fragments resulting from the disassembly of highly excited large thermal-like nuclear emitting sources, formed in the ^{197}Au + ^{197}Au reaction at 35 MeV/nucleon beam energy, are presented. Two different decay systems (the quasiprojectile formed in midperipheral reactions and the unique source coming from the incomplete fusion of projectile and target in the most central collisions) were considered; these emitting sources have the same initial N/Z ratio and excitation energy (E^* ~= 5--6 MeV/nucleon), but different size. Their charge yields and isotopic content of the fragments show different distributions. It is observed that the neutron content of intermediate mass fragments increases with the size of the source. These evidences are consistent with chemical equilibrium reached in the systems. This fact is confirmed by the analysis with the statistical multifragmentation model.Comment: 9 pages, 4 ps figure

    Scale setting for alpha_s beyond leading order

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    We present a general procedure for incorporating higher-order information into the scale-setting prescription of Brodsky, Lepage and Mackenzie. In particular, we show how to apply this prescription when the leading coefficient or coefficients in a series in the strong coupling alpha_s are anomalously small and the original prescription can give an unphysical scale. We give a general method for computing an optimum scale numerically, within dimensional regularization, and in cases when the coefficients of a series are known. We apply it to the heavy quark mass and energy renormalization in lattice NRQCD, and to a variety of known series. Among the latter, we find significant corrections to the scales for the ratio of e+e- to hadrons over muons, the ratio of the quark pole to MSbar mass, the semi-leptonic B-meson decay width, and the top decay width. Scales for the latter two decay widths, expressed in terms of MSbar masses, increase by factors of five and thirteen, respectively, substantially reducing the size of radiative corrections.Comment: 39 pages, 15 figures, 5 tables, LaTeX2

    Chiral and Gluon Condensates at Finite Temperature

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    We investigate the thermal behaviour of gluon and chiral condensates within an effective Lagrangian of pseudoscalar mesons coupled to a scalar glueball. This Lagrangian mimics the scale and chiral symmetries of QCD. (Submitted to Z. Phys. C)Comment: 20 pages + 7 figures (uuencoded compressed postscript files), University of Regensburg preprint TPR-94-1

    Double-Scaling Limit of Heterotic Bundles and Dynamical Deformation in CFT

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    We consider heterotic string theory on Eguchi-Hanson space, as a local model of a resolved A_1 singularity in a six-dimensional flux compactification, with an Abelian gauge bundle turned on and non-zero torsion. We show that in a suitable double scaling limit, that isolates the physics near the non-vanishing two-cycle, a worldsheet conformal field theory description can be found. It contains a heterotic coset whose target space is conformal to Eguchi-Hanson. Starting from the blow-down limit of the singularity, it can be viewed as a dynamical deformation of the near-horizon fivebrane background. We analyze in detail the spectrum of the theory in particular examples, as well as the important role of worldsheet non-perturbative effects.Comment: 45 pages, no figures; ver2: typos corrected, references added, an extra tadpole-free model covere

    Kreuth IV: European consensus proposals for treatment of haemophilia with coagulation factor concentrates

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    Introduction: This report summarizes recommendations relating to haemophilia therapy arising from discussions among experts from 36 European countries during the \ue2\u80\u98Kreuth IV\ue2\u80\u99 meeting in May 2016. Aim: The objective of the meeting was for experts in the field of haemophilia from across Europe to draft resolutions regarding current issues relating to the treatment of haemophilia. Results: Hospitals providing clinical care for people with haemophilia and related disorders are strongly recommended to seek formal designation as either European Haemophilia Treatment Centres (EHTC) or European Haemophilia Comprehensive Care Centres (EHCCC). There should be agreed national protocols or guidelines on management of the ageing patient with haemophilia. The minimum consumption of factor VIII and IX concentrate in any country should be 4 IU and 0.5 IU per capita of general population respectively. Treatment for hepatitis C with direct-acting antiviral agents should be provided to all people with haemophilia on a priority basis. Genotype analysis should be offered to all patients with severe haemophilia. Genetic counselling, when given, should encompass the recommendation that genetic relatives of the affected person be advised to seek genetic counselling. People with inhibitors should have access to bypassing agents, immune tolerance and elective surgery. National or regional tenders for factor concentrates are encouraged. Outcome data including health related quality of life should be collected. Treatment with extended half-life factors should be individualized and protection against bleeding should be improved by increasing trough levels. Steps should be taken to understand and minimize the risk of inhibitor development. Conclusion: It is hoped that these recommendations will help to foster equity of haemophilia care throughout Europe
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