On Some Subfactors of Integer Index Arising from Vertex Models

This paper is devoted to the study of subfactors arising out of commuting squares constructed out of the simplest possible vertex models. After setting up the necessary general background, we start with two classes of commuting squares and compute the principal graphs of the resulting subfactors, one of them being related to the group dual of a suitable (closed) subgroup ofU(N), and the other to the Cayley graph of a (non-closed) group, modulo scalars, generated byNelements ofU(N). In the last section, we “classify” the commuting squares in dimension 2, and identify the possible resulting principal graphs asA(1)(2n−1), 1⩽n⩽∞