Bonn 2010 – wissenschaftliches Programm
HK 51.1: Gruppenbericht
Donnerstag, 18. März 2010, 16:30–17:00, HG II
Thermodynamic quark susceptibilties in the PNJL model — •Marco Cristoforetti, Thomas Hell, Bertram Klein, and Wolfram Weise — Technische Universität München
The Monte-Carlo method is applied to the Polyakov-loop extended Nambu–Jona-Lasinio (PNJL) model. This allows to go beyond the saddle-point approximation in a mean-field calculation and introduces fluctuations around the mean fields. We study the impact of fluctuations on the thermodynamics of the model, both in the case of a pure gauge theory including two quark flavors. In the two-flavor case, we calculate the second order Taylor expansion coefficients of the thermodynamic grand canonical partition function with respect to quark chemical potential and present a comparison with extrapolations from lattice QCD. We show that the introduction of fluctuations produces only small changes in the behavior of the order parameters for the chiral restoration and the deconfinement transitions. On the other hand, we find that fluctuations are necessary in order to reproduce lattice data for the flavor non-diagonal expansion coefficients. Of particular importance are pion fields, the contribution of which is strictly zero in the saddle point approximation.