The many faces of Ocneanu cells Original Research Article

We define generalised chiral vertex operators covariant under the Ocneanu “double triangle algebra” A, a novel quantum symmetry intrinsic to a given rational 2d conformal field theory. This provides a chiral approach, which, unlike the conventional one, makes explicit various algebraic structures encountered previously in the study of these theories and of the associated critical lattice models, and thus allows their unified treatment. The triangular Ocneanu cells, the 3j-symbols of the weak Hopf algebra A, reappear in several guises. With A and its dual algebra  one associates a pair of graphs, G and G̃. While G are known to encode complete sets of conformal boundary states, the Ocneanu graphs G̃ classify twisted torus partition functions. The fusion algebra of the twist operators provides the data determining Â. The study of bulk field correlators in the presence of twists reveals that the Ocneanu graph quantum symmetry gives also an information on the field operator algebra.