Quantum-chromodynamic effects in a quark gas at finite temperature and density

We investigate the quark gas at finite temperatures and densities including nonperturbative effects in the framework of quantum chromodynamics. In our calculations we use the dilute-gas approximation for the thermodynamics of the finite-temperature instanton gas. For the suppression of large-scale instantons we consider the color-charge screening. The nonperturbative results can be compared directly from our numerical evaluations with those of the perturbation calculations