Axial anomaly, vector meson dominance and π0→γγ at finite temperature

A thermal Finite Energy QCD Sum Rule is used to determine the temperature behaviour of the ωρπ strong coupling. This coupling decreases with increasing T and vanishes at the critical temperature, a likely signal for quark deconfinement. This is then used in the Vector Meson Dominance (VMD) expression for the π0→γγ amplitude, which is also found to vanish at the critical temperature, as expected. This result supports the validity of VMD at T≠0. However, if VMD would not hold at finite temperature, then there is no prediction for the π0→γγ amplitude.