Anomalous $U(1)_A$ couplings and the Columbia plot
Anomalous $U(1)_A$ couplings and the Columbia plot
When the quark masses are lighter than those in QCD, the standard lore is that a chiral transition of first order must emerge for three, light flavors. Recently, however, numerical simulations on the lattice suggest that the chiral transition is of second order in the chiral limit. Using an extended …