Bloch-Nordsieck propagator at finite temperature

We have shown recently that the resummation of soft photon contributions leads to a nonexponential decay of the fermion excitations in hot QED plasmas. The retarded propagator of a massless fermion was found to behave as S-R(t much greater than 1/gT)similar to exp{-alpha Tt[ln omega(p)t+C]}, where omega(p) = gT/3 is the plasma frequency, alpha = g(2)/4 pi, and C is a constant, independent of g, which was left undefined. This term is computed in this paper. In gauges with unphysical degrees of freedom, it is gauge-fixing independent provided an infrared regulator is introduced in the gauge sector. We also extend our analysis to hot QCD and express the quark and gluon propagators in the form of three-dimensional Euclidean functional integrals which may be evaluated on the lattice. [S0556-2821(97)00624-3].