On the fluctuation–dissipation theorem for soft fermionic excitations in a hot QCD plasma

Abstract

We discuss two ways of deriving the fluctuation–dissipation theorem (FDT) for soft fermion excitations in a hot non-Abelian plasma being in a thermal equilibrium. The first of them is based on the extended (pseudo)classical model in describing a quark–gluon plasma suggested in [Yu.A. Markov, M.A. Markova, Nucl. Phys. B 784 (2007) 443], while the second one rests on the standard technique of calculation of the FDT for thermodynamically equilibrium systems. We show that full accounting all subtleties that are common to the fermion system under consideration, results in perfect coincidence of thus obtained FDTs. This provides a rather strong argument for the validity of the pseudoclassical model suggested.