Topology in the SU(N_f) chiral symmetry restored phase of unquenched QCD and axion cosmology. Ⅱ.

摘要

We investigate the physical consequences of the survival of the effects of the U(1)_A anomaly in the chiral symmetric phase of QCD, and show that the free energy density is a singular function of the quark mass m, in the chiral limit, and that the σ and π susceptibilities diverge in this limit at any T ≥ T_c.We also show that the difference between the π and δ susceptibilities diverges in the chiral limit at any T ≥ T_c, a result which seems to be excluded by recent results of Tomiya et al. from numerical simulations of two-flavor QCD. We also discuss on the generalization of these results to the N_f ≥ 3 model.