ANALYTICAL SOLUTION OF THE 2D CLASSICAL HEISENBERG-MODEL

For the first time we exactly establish the term of higher degree in t he polynomial expansion of the zero-field partition function. In the i nfinite-layer limit, we derive analytical expressions for the spin-spi n correlations, the susceptibility and the specific heat, and we exami ne their respective behaviours near the critical temperature T-c = OK. We calculate the analytical values of critical exponents alpha,gamma, eta and nu.