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

A thermal QCD Finite Energy Sum Rule (FESR) is used to obtain the temperatu re 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 les s than or equal to T less than or equal to 0.9 T-c, where T-c is the critic al 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 as sociated with g(A) and find that it diverges at T = T-c, thus signalling qu ark deconfinement. As a byproduct, we study the temperature dependence of t he Goldberger-Treiman relation. (C) 1999 Published by Elsevier Science B.V. All rights reserved.