Effektive Wirkungen fuer QCD bei hoher Temperatur

Nearly ten years ago Braaten and Pisarski succeeded to establish a reliable perturbation series for gauge theories at high temperature. With their resummation scheme several up to that point unaccessible quantities could be calculated, e.g. the damping of excitations in a quark-gluon-plasma. But a few problems remained. Infrared divergencies due to the lack of a 'magnetic mass' are not completely understood as well as collinear divergencies in quantities which depend on lightlike momenta. This thesis solves the latter problem. An improvement of the action by Braaten and Pisarski is presented which contains no more collinear singularities. This is achieved by an additional resummation of a certain 'asymptotic' mass. It is prooved that such a resummation is mandatory whenever outer momenta are light-like. The uniqueness of the action is discussed. Finally the calculation of the real soft photon-production rate is re-investigated and instead of the know singular result a finite one is obtained. (orig.)SIGLEAvailable from TIB Hannover: RR 8919(1998,001) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman