343 research outputs found

    Exact Classical and Quantum Dynamics in Background Electromagnetic Fields

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    Analytic results for (Q)ED processes in external fields are limited to a few special cases, such as plane waves. However, the strong focussing of intense laser fields implies a need to go beyond the plane wave model. By exploiting Poincar\'e symmetry and superintegrability we show how to construct, and solve without approximation, new models of laser-particle interactions. We illustrate the method with a model of a radially polarised (TM) laser beam, for which we exactly determine the classical orbits and quantum wave functions. Including in this way the effects of transverse field structure should improve predictions and analyses for experiments at intense laser facilities.Comment: 6 pages, 3 pdf figure

    A novel approach to light-front perturbation theory

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    We suggest a possible algorithm to calculate one-loop n-point functions within a variant of light-front perturbation theory. The key ingredients are the covariant Passarino-Veltman scheme and a surprising integration formula that localises Feynman integrals at vanishing longitudinal momentum. The resulting expressions are generalisations of Weinberg's infinite-momentum results and are manifestly Lorentz invariant. For n = 2 and 3 we explicitly show how to relate those to light-front integrals with standard energy denominators. All expressions are rendered finite by means of transverse dimensional regularisation.Comment: 10 pages, 5 figure

    The Relationship of Collaboration Technologies and Cognition and Affect

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    The Relationship of Collaboration Technologies and Cognition and Affect

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    Practice Impact of IS Research

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    Classical and quantum particle dynamics in univariate background fields

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    We investigate deviations from the plane wave model in the interaction of charged particles with strong electromagnetic fields. A general result is that integrability of the dynamics is lost when going from lightlike to timelike or spacelike field dependence. For a special scenario in the classical regime we show how the radiation spectrum in the spacelike (undulator) case becomes well-approximated by the plane wave model in the high energy limit, despite the two systems being Lorentz inequivalent. In the quantum problem, there is no analogue of the WKB-exact Volkov solution. Nevertheless, WKB and uniform-WKB approaches give good approximations in all cases considered. Other approaches that reduce the underlying differential equations from second to first order are found to miss the correct physics for situations corresponding to barrier transmission and wide-angle scattering.Comment: 12 pages, 8 figure

    Spontaneous symmetry breaking of (1+1)-dimensional Ď•4\bf \phi^4 theory in light-front field theory (III)

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    We investigate (1+1)-dimensional Ď•4\phi^4 field theory in the symmetric and broken phases using discrete light-front quantization. We calculate the perturbative solution of the zero-mode constraint equation for both the symmetric and broken phases and show that standard renormalization of the theory yields finite results. We study the perturbative zero-mode contribution to two diagrams and show that the light-front formulation gives the same result as the equal-time formulation. In the broken phase of the theory, we obtain the nonperturbative solutions of the constraint equation and confirm our previous speculation that the critical coupling is logarithmically divergent. We discuss the renormalization of this divergence but are not able to find a satisfactory nonperturbative technique. Finally we investigate properties that are insensitive to this divergence, calculate the critical exponent of the theory, and find agreement with mean field theory as expected.Comment: 21 pages; OHSTPY-HEP-TH-94-014 and DOE/ER/01545-6

    Success in offshoring of application development – does culture matter?

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    Recently, offshoring of information systems (IS) services to external vendors has seen considerable growth. Outsourcing to vendors in foreign countries brings about unique challenges which need to be understood and managed effectively. This paper explores cultural differences in IS offshoring arrangements involving German client organizations that outsource application development activities to Indian vendors. For this purpose, a research framework is developed based on both theoretical considerations and specific empirical observations from multiple case studies. The goal is to (1) explore the nature of cultural differences in offshoring arrangements in depth and to (2) analyze the relationship between those cultural differences and offshoring success. Based on the case findings, implications and practices for the management of offshore development projects are outlined
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