Fermion Spectrum at Ultrasoft Region in a Hot QED/QCD Plasma

摘要

A spectrum of an electron (quark) with ultrasoft momentum (p ～ g~2T) is discussed at extremely high temperature in quantum electrodynamics (chromodynamics) with a resummed perturbation theory. We establish the existence of the pole suggested in the previous work of the electron (quark) propagator at the ultrasoft region and find that its pole position is p_0 = -+|p|/3 - iζ, where ζ is the damping rate which is of order g~2T ln 1/g, and the expression of its residue. We also discuss whether the resummation scheme preserves the gauge symmetry.