HOW PI(0)-]GAMMA-GAMMA CHANGES WITH TEMPERATURE

At zero temperature, in the chiral limit the amplitude for pi(0) to de cay into two photons is directly related to the coefficient of the axi al anomaly. At any nonzero temperature, this direct relationship is lo st: while the coefficient of the axial anomaly is independent of tempe rature, in a thermal bath the anomalous Ward identities do not uniquel y constrain the amplitude for pi(0)-->gamma gamma. Explicit calculatio n shows that to lowest order about zero temperature this amplitude dec reases. [S0556-2821(97)00423-2].