[RBRC seminar] Order of the QCD chiral phase transition in the chiral limit

by Prof. Gergely Fejos (Eotvos university)

Thursday 5 Nov 2026, 13:00 → 15:00 US/Eastern

2-160 (https://bnl.zoomgov.com/j/1600983728?pwd=RAD7OLcqre7Ycsp6JfFp6HAnpyLxex.1)

The order of the chiral phase transition for massless quarks remains an open problem. The perturbative renormalization group in the ε-expansion predicts a fluctuation-induced first-order transition for N_f ≥ 3, and also for N_f = 2 if the U(1)_A anomaly is effectively restored at the critical temperature. Lattice simulations, by contrast, have found the first-order region of the Columbia plot shrinking as the continuum limit is approached, with no clear signal of a first-order transition toward the chiral limit. I will discuss how the functional renormalization group, applied directly in three dimensions, may resolve this tension. I will show that a stable infrared fixed point can exist, making the transition second order for any number of flavors, with the outcome controlled by the strength of the axial anomaly near the transition temperature.