QCD sum rule determination of the axial-vector coupling of the nucleon at finite temperature

Abstract A thermal QCD Finite Energy Sum Rule (FESR) is used to obtain the temperature dependence of the axial-vector coupling of the nucleon, g A ( T ). We find that g A ( T ) is essentially independent of T , in the very wide range 0≤T≤0.9 T c , where T c is the critical temperature. While g A at T =0 is q 2 -independent, it develops a q 2 dependence at finite temperature. We then obtain the mean square radius associated with g A and find that it diverges at T = T c , thus signalling quark deconfinement. As a byproduct, we study the temperature dependence of the Goldberger-Treiman relation.