  We apply a Monte-Carlo method to the two flavor Polyakov loop extended Nambu
and Jona-Lasinio (PNJL) model. In such a way we can go beyond mean field
calculations introducing fluctuations of the fields. We study the impact of
fluctuations on the thermodynamics of the model. We calculate the second
derivatives of the thermodynamic grand canonical partition function with
respect to the chemical potential and present a comparison with lattice data
also for flavor non-diagonal susceptibilities.
