Discrete approximations to vector spin models
  We strengthen a result of two of us on the existence of effective interactions for discretised continuous-spin models. We also point out that such an interaction cannot exist at very low temperatures. Moreover, we compare two ways of discretising continuous-spin models, and show that, except for very low temperatures, they behave similarly in two dimensions. We also discuss some possibilities in higher dimensions. 
A. C. D. van Enter, C. Kuelske, A. A. Opoku
math-ph math.MP