SU(3) latent heat and surface tension from tree level and tadpole improved actions

We analyze the latent heat and surface tension at the SU(3) deconfinement phase transition with tree level and tadpole improved Symanzik actions on lattices with temporal extent N-tau = 3 and 4 and spatial extent N-sigma/N-tau = 4, 6 and 8. In comparison to the standard Wilson action we do find a drastic reduction of cut-off effects already with tree level improved actions. On lattices with temporal extent N-tau = 4 results for the surface tension and latent heat obtained with a tree level improved action agree well with those obtained with a tadpole improved action. A comparison with N-tau = 3 calculations, however, shows that results obtained with tadpole action remain unaffected by cut-off effects even on this coarse lattice, while the tree level action becomes sensitive to the cut-off. For the surface tension and latent heat we find sigma(1)/T-c(3) = 0.0155 (16) and Delta epsilon/T-c(4) = 1.40 (9), respectively.