The chiral phase transition and the role of vacuum fluctuations

Abstract

We apply optimized perturbation theory to the quark–meson model at finite temperature [Formula: see text] and quark chemical potential [Formula: see text]. The effective potential is calculated to one loop both in the chiral limit and at the physical point and used to study the chiral dynamics of two-flavor QCD. The critical temperature and the order of the phase transition depend heavily on whether or not one includes the bosonic and fermionic vacuum fluctuations in the effective potential. A full one-loop calculation in the chiral limit predicts a first-order transition for all values of [Formula: see text]. At the physical point, one finds a crossover in the whole [Formula: see text]–[Formula: see text] plane.