Symmetry and correlation functions in the high temperature phase of QCD

Simple group-theoretical arguments are used to demonstrate that in the high temperature (chirally restored) phase of QCD with Nf massless flavours, all n-point correlation functions of quark bilinears are invariant under U(1)A transformations provided n < Nf. In particular this implies that the two-point correlation function in the η′ channel is identical to that in the pion channel for Nf > 2. Unlike previous work, this result does not depend on the topological properties of QCD and can be formulated without explicit reference to functional integrals.