Phase Structure of Hot and/or Dense QCD with the Schwinger-Dyson Equation

We investigate the phase structure of hot and/or dense QCD using the Schwinger-Dyson equation (SDE) with the improved ladder approximation in the Landau gauge. We show that the phase transition from the two-flavor color superconducting (2SC) phase to the quark-gluon plasma (QGP) phase is of second order, and that the scaling properties of the Majorana mass gap and the diquark condensate are consistent with the mean field scaling. We examine the effect of antiquark contribution, and find that setting the antiquark Majorana mass equal to the quark one is a good approximation in the medium density region. We also study the effect of the Debye screening mass of gluon, and find that neglection of it moves the critical lines to the higher temperature and higher chemical potential region