Speaker
Sinya Aoki
(Kyoto University)
Description
We discuss the fate of the axial U(1) symmetry in 2-flavor QCD, when the non-singlet chiral symmetries are recovered at finite temperature. We theoretically investigate the constraints on the eigenvalue density of the Dirac operator, derived from the non-singlet chiral symmetries among various multi-point correlation functions in the chiral limit. We show that the axial U(1) symmetry, broken by the anomaly at low temperature, is "effectively" recovered in the chiral symmetric phases of 2-flavor QCD above the critical temperature. Here the effective recovery of the axial U(1) symmetry means, for example, that the susceptibility of non-singlet (pi) and singlet (eta) pseudo-scalar mesons become identical in the symmetric phase, which implies that the axial U(1) anomaly is invisible in these channels. We next consider recent numerical investigations on the axial U(1) symmetry in 2-flavor lattice QCD with exact lattice chiral symmetry, which is shown to be crucial for this problem. Numerical results in these study confirm our theoretical expectation mentioned above. We finally discuss an implication of our results to the phase structure of lattice QCD at finite temperature.
Primary author
Sinya Aoki
(Kyoto University)
