Infrared divergences, mass shell singularities and gauge dependence of   the dynamical fermion mass
  We study the behavior of the dynamical fermion mass when infrared divergences and mass shell singularities are present in a gauge theory. In particular, in the massive Schwinger model in covariant gauges we find that the pole of the fermion propagator is divergent and gauge dependent at one loop, but the leading singularities cancel in the quenched rainbow approximation. On the other hand, in physical gauges, we find that the dynamical fermion mass is finite and gauge independent at least up to one loop. 
Ashok K. Das, J. Frenkel and C. Schubert
hep-th