STRONG-COUPLING EXPANSION IN LATTICE QCD AT FINITE TEMPERATURE AND FINITE BARYON DENSITY

By means of the strong-coupling expansion an analytic study is made of the restoration of chiral symmetry in lattice QCD at finite temperature and finite baryon-number density, and the order of the phase transition is predicted. By means of the 1/d expansion an effective action for QCD is derived with the color group SU(3) in d-dimensional space at a finite large coupling constant and at finite temperature and chemical potential-mu. It is shown that the inclusion of baryons leaves the phase picture corresponding to mu = 0 almost unchanged, and that in full QCD (with mesons and baryons) the second-order chiral phase transition, discovered previously in QCD without baryons, exists. A second-order chiral phase transition is found at mu = mu-c and at arbitrary low temperature.