IMPROVED ACTIONS FOR QCD THERMODYNAMICS ON THE LATTICE

Finite cut-off effects strongly influence the thermodynamics of lattic e regularized QCD at high temperature in the standard Wilson formulati on. We analyze the reduction of finite cut-off effects in formulations of the thermodynamics of SU(N) gauge theories with three different O( a(2)) and O(a(4)) improved actions. We calculate the energy density an d pressure on finite lattices in leading order weak coupling perturbat ion theory (T --> infinity) and perform Monte Carlo simulations with i mproved SU(3) actions at non-zero g(2). Already on lattices with tempo ral extent N-tau = 4 we find a strong reduction of finite cut-off effe cts in the high temperature limit, which persists also down to tempera tures a few times the deconfinement transition temperature.