DOI 10.1007/s100529901095
Interpretation and resolution of pinch singularities in non-equilibrium quantum field theory
Institut für Theoretische Physik, Universität Giessen, D-35392 Giessen, Germany
Received: 28 September 1998 / Published online: 11 March 1999
Abstract
Ill-defined pinch singularities arising
in a perturbative expansion in out of equilibrium quantum field
theory have a natural analogue to standard scattering theory.
We explicitly demonstrate that the occurrence of such terms is directly related
to Fermi's golden rule known from elementary scattering theory and is thus
of no mystery.
We further argue that within the process of thermalization of a plasma
one has to resum such contributions to all orders as the process itself
is of non-perturbative nature. In this way the resummed propagators obtain
a finite width. Within the Markov approximation of kinetic theory
the actual phase space distribution
at a given time of the evolution enters explicitly.
Copyright Springer-Verlag
