The chiral phase transition and the role of vacuum fluctuations

TL;DR

This paper investigates how vacuum fluctuations influence the chiral phase transition in two-flavor QCD using optimized perturbation theory, revealing that their inclusion determines whether the transition is first-order or a crossover.

Contribution

It provides a detailed one-loop analysis of the chiral phase transition in the quark-meson model, highlighting the impact of vacuum fluctuations on the transition's nature.

Findings

Vacuum fluctuations significantly affect the order of the phase transition.

In the chiral limit, a first-order transition is predicted for all chemical potentials.

At the physical point, the transition is a crossover across the entire temperature-chemical potential plane.

Abstract

We apply optimized perturbation theory to the quark-meson model at finite temperature T and quark chemical potential mu. 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 depends 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 mu. At the physical point, one finds a crossover in the whole $\mu-T$ plane.