QCD - NLC

We give a status report of our current theoretical work on QCD near the light-cone.Comment: 10 pages, Talk given at Three Days of Hadronic Physics (HLPR04): Joint Meeting Heidelberg-Liege-Paris-Rostock, Liege, Belgium, 16-18 Dec 2004. Published in AIP Conf.Proc.775:252,200

Hamiltonian Flow Equations for the Lipkin Model

We derive Hamiltonian flow equations giving the evolution of the Lipkin Hamiltonian to a diagonal form using continuous unitary transformations. To close the system of flow equations, we present two different schemes. First we linearize an operator with three pairs of creation and destruction operators by reducing it to the $z$ component of the quasi spin. We obtain the well known RPA-result in the limit of large particle number. In the second scheme we introduce a new operator which improves the resulting spectrum considerably especially for few particles.Comment: 10 pages, 2 eps figures, uses article.sty, epsfig.st

RG flow of the Polyakov-loop potential: First status report

We study SU(2) Yang-Mills theory at finite temperature in the framework of the functional renormalization group. We concentrate on the effective potential for the Polyakov loop which serves as an order parameter for confinement. In this first status report, we focus on the behaviour of the effective Polyakov-loop potential at high temperatures. In addition to the standard perturbative result, our findings provide information about the ``RG improved'' backreactions of Polyakov-loop fluctuations on the potential. We demonstrate that these fluctuations establish the convexity of the effective potential.Comment: 10 pages, 2 figure