Daniel Zwanziger

Publications (3)0 Total impact

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  Available from: Lichtenegger Klaus

  Article: Infrared Critical Exponents in Finite-Temperature Coulomb Gauge QCD

  Klaus Lichtenegger, Daniel Zwanziger
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  ABSTRACT: We investigate the infrared critical exponents of Coulomb gauge Yang-Mills theory in the limit of very high temperature. This allows us to focus on one scale (the spatial momentum) since all but the lowest Matsubara frequency decouple from the deep infrared. From the first-order Dyson-Schwinger equations in a bare-vertex truncation we obtain infrared exponents which correspond to confining or overconfining (yet mathematically well-defined) solutions. For three spatial dimensions the exponents are close to what is expected for a linearly rising color-Coulomb potential. Comment: 16 pages, 6 figures
  11/2009;
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  Available from: Lichtenegger Klaus

  Article: Contributions to the QCD Pressure Beyond Perturbation Theory

  Klaus Lichtenegger, Daniel Zwanziger
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  ABSTRACT: In this article we report on a new proposal to treat the infrared problems of thermal QCD by taking into account explicitly the confining influence of the Gribov horizon. In order to make clear the possible value of such an approach, we briefly review the most important arguments why a straightforward perturbative description of finite-temperature QCD is unlikely to be successful. From the infrared problems of thermal perturbation theory one can conclude that confinement effects and bound states probably play an important role also in the high-temperature phase. To set the stage we recount the supposed role of the Gribov horizon for confinement, before we turn to the application to finite-temperature theory. In the current approach it has been found that the contributions to the free energy from the explicit inclusion of the horizon begin to set in at order $g^6$ -- precisely where the infrared problems of thermal QCD lead to a breakdown of ordinary perturbation theory. From the study of observables (free energy, anomaly, bulk viscosity) we also note that for thermodynamic observables the leading order term obtained by such an expansion in the coupling strongly deviates from the more complete numerical solution. This can be regarded as yet another sign for general problems of series expansions in thermal QCD. Comment: 5 pages, to appear in the proceedings of Confinement 8, 2008 in Mainz
  12/2008;
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  Available from: Lichtenegger Klaus

  Article: Nonperturbative contributions to the QCD pressure

  Klaus Lichtenegger, Daniel Zwanziger
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  ABSTRACT: We summarize the most important arguments why a perturbative description of finite-temperature QCD is unlikely to be possible and review various well-established approaches to deal with this problem. Then, using a recently proposed method, we investigate nonperturbative contributions to the QCD pressure and other observables (like energy, anomaly and bulk viscosity) obtained by imposing a functional cutoff at the Gribov horizon. Finally, we discuss how such contributions fit into the picture of consecutive effective theories, as proposed by Braaten and Nieto, and give an outline of the next steps necessary to improve this type of calculation.
  06/2008;