Curvature of the QCD phase transition line in a finite volume

Abstract

Karl-Franzens-Universitat GrazE-mail: bernd-jochen.schaefer@uni-graz.atThe curvature which characterizes the QCD phase transition at finite temperature and smallvalues of the chemical potential is accessible to lattice simulations. The results for this quantitywhich have been obtained by several different lattice simulation methods differ due to differ-ent numbers of flavors, different pion masses and different sizes of the simulation volume. Inorder to reconcile these results, it is important to investigate finite-volume effects on the curvature.We investigate the curvature of the chiral phase transition line at finite temperature and chemicalpotential in a finite volume. We use a phenomenological model for chiral symmetry breakingand apply non-perturbative functional renormalization group methods which account for criticallong-range fluctuations at the phase transition.We find an intermediate volume region in which the curvature of the phase transition line is ac-tually reduced relative to its infinite-volume value, provided periodic spatial boundary conditionsare chosen for the quark fields. Size and location of this region depend on the value of the pionmass. Such an effect could account for differences in the curvature between lattice simulations indifferently sized volumes and from functional methods in the infinite volume limit. We discussimplications of our results for the QCD phase diagram.The XXVIII International Symposium on Lattice Field Theory, Lattice2010June 14-19, 2010Villasimius, Italy