By means of a formal expression of the Cornwall-Jackiw-Tomboulis effective
potential for quark propagator at finite temperature and finite quark chemical
potential, we derive the real-time thermal Schwinger-Dyson equation for quark
propagator in Landau gauge. Denote the inverse quark propagator by
A(p2)î€ p−B(p2), we argue that, when temperature T is less than the
given infrared momentum cutoff pc​, A(p2)=1 is a feasible approximation
and can be assumed in discussions of chiral symmetry phase transition problem
in QCD.Comment: 8 pages, Latex, no figur