HIGH-TEMPERATURE SERIES EXPANSIONS FOR THE (2 + 1)-DIMENSIONAL ISING-MODEL

Using efficient cluster expansion methods, the known high-temperature series for the vacuum energy, specific heat, susceptibility and mass gap of the (2+1)-dimensional Ising model on the square and triangular lattices have been extended by several terms. Estimates of the critical indices demonstrate very convincing universality with the Euclidean version of the model.