Gluon propagator in Feynman gauge by the method of stationary variance

The low-energy limit of pure Yang-Mills SU(3) gauge theory is studied in Feynman gauge by themethod of stationary variance, a genuine second-order variational method that is suited to deal with theminimal coupling of fermions in gauge theories. In terms of standard irreducible graphs, the stationaryequations are written as a set of coupled nonlinear integral equations for the gluon and ghost propagators.A physically sensible solution is found for any strength of the coupling. The gluon propagator is finite inthe infrared, with a dynamical mass that decreases as a power at high energies. At variance with some recentfindings in Feynman gauge, the ghost dressing function does not vanish in the infrared limit and adecoupling scenario emerges as recently reported for the Landau gauge.