The Dyson-Schwinger equation for the quark self energy is solved in rainbow approximation using an infrared (IR) vanishing gluon propagator that introduces an IR mass scale b. For realistic QCD coupling constants the strength and the scale of spontaneous chiral symmetry breaking decouple from the IR scale b. At timelike momenta the quark propagator possesses a pole proving that quarks are not confined in this model. We argue that the quark propagator is analytic within the whole complex momentum plane except on the timelike axis. It is demonstrated that in models using rainbow approximation and gluon propagators which are symmetric under the exchange of spacelike and timelike momenta quark confinement and Wick rotation exclude each other.
20 pages
e-mail: alkofer@ptsun1.tphys.physik.uni-tuebingen.de