The axial anomaly in QCD at finite temperature

We study flavor mixing and the U(1)A anomaly in QCD at zero and finite temperature. Using the instanton liquid model, we show that the strength of the anomaly is essentially unchanged near the critical temperature for chiral symmetry restoration. We demonstrate that nevertheless chiral symmetry restoration has important consequences for the η and η′. In particular, the strange and non-strange components of the η unmix near Tc. The anomaly does not affect the strange eta, so we expect a light purely strange pseudoscalar near the phase transition.