SPIN MODELS CORRESPONDING TO NONSYMMETRIC ASSOCIATION SCHEMES OF CLASS 2

Abstract

In [6] Yasuo Watatani and Akihiro Munemasa found an example of a nonsymmetric spin model on 3 vertices. In this paper we show that there are no spin models corresponding to nonsymmetric association schemes of class 2 except the ones corresponding to Potts models and the one on three vertices.