CRITICAL EXPONENTS AND CORRECTIONS TO SCALING .1. 3D HEISENBERG-MODEL

The functions H/M=K(T,M2) and T(K,M2) are investigated near the critical point. It is shown that the coefficients in expansions of scaling functions and in corrections to scaling may be chosen in such a way that the functions k(T,M2) and T(K,M2) are analytic in the variable M2 even at T=0 and K=0, respectively, contrary to the scaling law. On the basis of high-temperature expansion results, it is shown in three different ways that analyticities are fulfilled for the three-dimensional Heisenberg model. Postulating the two analyticities, it is concluded that beta =1/2 and delta =5 for that model. Postulates are generalised for other models. It is shown that all critical exponent estimate sets that are known exactly can be obtained on the basis of the two postulates which can be regarded as the basis of a generalised Landau theory.