Topology in the SU(Nf) chiral symmetry restored phase of unquenched QCD and axion cosmology. II.
AbstractWe 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≥Tc. We also show that the difference between the π¯ and δ¯ susceptibilities diverges in the chiral limit at any T≥Tc, 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 Nf≥3 model.