Phase Structure of Hot and/or Dense QCD in the Schwinger-Dyson Approach

We investigate the phase structure of hot and/or dense QCD with massless 2-flavors using the Schwinger-Dyson equation (SDE) with the improved ladder approximation in the Landau gauge. We examine the effect of the antiquark contribution and find that setting the antiquark Majorana mass equal to the quark one is a good approximation in the medium density region. The imaginary part of the Dirac mass has an important influence on the chiral phase transition, in particular on the tricritical point.