  We show a gauge parameter dependence of the 1-loop fermion self energy at
finite temperature before the analytic continuation. We also show a gauge
parameter dependence of only the temperature dependence term. The result is the
same as the ladder approximation Schwinger-Dyson equation. The wave function
renormalization constant approaches 1 by taking a negative gauge parameter. The
analogy of the ladder approximation Schwinger-Dyson equation and the 1-loop
calculation will help the analysis of the phase transition.
