A correlation function renormalization group analysis of the ferromagnetic transition in theZ n spin model

Summary In theZ _n spin model on a finite square lattice of only eight sites, correlation functions are calculated and used for implementing a renormalization transformation for 2≤n≤10. Estimates for critical points and thermal and magnetic exponents are found in fair agreement with exact or Monte Carlo results. Forn≥5 the method describes rather accurately the ferromagnetic critical point at the bottom of the massless phase. Senior Research Assistant of the National Fund for Scientific Research Belgium.