7,892 research outputs found

    Next-to-leading order numerical calculations in Coulomb gauge

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    Calculations of observables in quantum chromodynamics can be performed using a method in which all of the integrations, including integrations over virtual loop momenta, are performed numerically. We use the flexibility inherent in this method in order to perform next-to-leading order calculations for event shape variables in electron-positron annihilation in Coulomb gauge. The use of Coulomb gauge provides the potential to go beyond a purely order alpha_s^2 calculation by including, for instance, renormalon or parton showering effects. We expect that the approximations needed to include such effects at all orders in alpha_s will be simplest in a gauge in which unphysically polarized gluons do not propagate over long distances.Comment: 36 pages with 7 figure

    QCD Calculations by Numerical Integration

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    Calculations of observables in Quantum Chromodynamics are typically performed using a method that combines numerical integrations over the momenta of final state particles with analytical integrations over the momenta of virtual particles. I discuss a method for performing all of the integrations numerically.Comment: 9 pages including 2 figures. RevTe

    Choosing integration points for QCD calculations by numerical integration

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    I discuss how to sample the space of parton momenta in order to best perform the numerical integrations that lead to a calculation of three jet cross sections and similar observables in electron-positron annihilation.Comment: 25 pages with 8 figure

    Diffraction in DIS and Elsewhere

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    I review some of the results presented in the working group on diffraction at DIS97, with a particular emphasis on the theory of diffractive hard scattering.Comment: Talk at DIS97 Conference, Chicago, April 1997. Eleven pages including nine figure

    Radical re-appraisal of water structure in hydrophilic confinement

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    The structure of water confined in MCM41 silica cylindrical pores is studied to determine if confined water really is simply a version of the bulk liquid which can be substantially supercooled without crystallisation. A combination of total neutron scattering from the porous silica, both wet and dry,and computer simulation using a realistic model of the scattering substrate isused. The water in the pore is divided into three regions: core, interfacial and overlap. The average local densities of water in these simulations are found to be about 20% lower than bulk water density, while the density in the core region is below, but closer to, the bulk density. There is a decrease in both local and core densities when the temperature is lowered from 298K to 210K. The radical proposal is made here that water in hydrophilic confinement is under significant tension, around -100MPa, inside the pore

    Basics of QCD Perturbation Theory: TASI 2000

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    This is an introduction to the use of QCD perturbation theory, emphasizing generic features of the theory that enable one to separate short-time and long-time effects. I also cover some important classes of applications: electron-positron annihilation to hadrons, deeply inelastic scattering, and hard processes in hadron-hadron collisions.Comment: Lectures at TASI summer school, June 200

    An interactive approach to learning economics: The WinEcon package

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    Under the TLTP initiative, the Economics Consortium is developing an interactive computer‐based learning package called WinEcon. The package is directed at first‐year economics undergraduates, particularly those taking economics as a supplementary course. Using recent technological developments, the aim is both to facilitate a further increase in student numbers without a proportionate increase in teaching staff, and to provide a better method of student learning. Some key elements of WinEcon are set out in this paper and demonstrated by screens produced at Leicester University. Methods of presenting textual information that give the user control over accessing it are described. For learning difficult concepts, a visual active learning approach is discussed. It involves user interaction and step‐by‐step analysis. The importance of flexibility and choice is emphasized, and the capacity of the computer to assist in deepening and consolidating learning is shown