Chiral versus deconfinement properties of the QCD crossover: Differences in the volume and chemical potential dependence from the lattice

Abstract

The crossover from hadronic to quark matter is understood to be both a deconfinement as well as a chiral symmetry–restoring transition. The precise definition of these aspects may be ambiguous. Here we use the static quark free energy and its temperature derivative as proxies for deconfinement and the chiral condensate and its mass derivatives for the chiral transition. At zero baryochemical potential, and infinite volume, the chiral and deconfinement crossover temperatures almost agree. However, as we vary the spatial volume of the simulation, we observe that chiral and deconfinement-related observables have a qualitatively different chemical potential and volume dependence. In general, deconfinement-related observables have a milder volume dependence. Furthermore, while the deconfinement transition appears to get broader with increasing μB, the width as well as the strength of the chiral transition is approximately constant. Our results are based on simulations at zero and imaginary chemical potentials using 4-stout-improved staggered fermions with Nτ=12 time slices and physical quark masses. Published by the American Physical Society 2025