  Some recent theoretical developments of the QCD phase diagram are summarized.
Chiral symmetry restoration and the confinement/deconfinement transition at
nonzero temperature and quark densities are analyzed in the framework of an
effective linear sigma model with three light quark flavors. The sensitivity of
the chiral transition as well as the existence of a critical end point in the
phase diagram on the value of the sigma mass is explored. The influence of the
axial anomaly on the chiral critical surface is addressed. Finally, the
modifications by the inclusion of the Polyakov loop on the phase structure are
investigated.
