Thermodynamics of Four-Flavour QCD with Improved Staggered Fermions

We have calculated the pressure and energy density in four-flavour QCD using improved fermion and gauge actions. We observe a strong reduction of finite cut-off effects in the high temperature regime, similar to what has been noted before for the SU(3) gauge theory. Calculations have been performed on 16(3) x 4 and 16(4) lattices for two values of the quark mass, ma = 0.05 and 0.1. A calculation of the string tension at zero temperature yields a critical temperature T-c/root sigma = 0.407 +/- 0.010 for the smaller quark mass value. (C) 1997 Elsevier Science B.V.