Chiral phase transitions in QCD for finite temperature and density

We study the diagram for the chiral phases of QCD on the plane of temperature and chemical potential. The calculation is based on the extension of a composite-operator formalism already employed for zero temperature and density. We find that, moving along the critical line for increasing chemical potential, one encounters a point separating second-order and first-order chiral phase transitions. The overall phase diagram is found to qualitatively reproduce the pattern for the Gross-Neveu model. Our study suggests the occurrence of metastable phases.