Me. Carrington et R. Kobes, GENERAL CANCELLATION OF LADDER GRAPHS AT FINITE-TEMPERATURE, Physical review. D. Particles and fields, 57(10), 1998, pp. 6372-6385
some cases, an important example being at finite temperature, extreme
infrared, collinear, or light-cone behavior may cause the usual loop-e
xpansion to break down. For some of these cases higher order ladder gr
aphs can become important. In all earlier paper it was shown that, giv
en a particular relation between a vertex and a self-energy function,
the resummation of the ladder graphs simplifies significantly when oth
er types of graphs are included in a consistent effective expansion. I
n this paper we show that this assumed relation is valid for a large c
lass of vertex and self-energy functions-at finite temperature.