paper

On -induction, chiral generators and modular invariants for subfactors

arXiv:math/9904109 · doi:10.1007/s002200050765

Abstract

We consider a type III subfactor of finite index with a finite system of braided - morphisms which includes the irreducible constituents of the dual canonical endomorphism. We apply -induction and, developing further some ideas of Ocneanu, we define chiral generators for the double triangle algebra. Using a new concept of intertwining braiding fusion relations, we show that the chiral generators can be naturally identified with the -induced sectors. A matrix is defined and shown to commute with the S- and T-matrices arising from the braiding. If the braiding is non-degenerate, then is a ``modular invariant mass matrix'' in the usual sense of conformal field theory. We show that in that case the fusion rule algebra of the dual system of - morphisms is generated by the images of both kinds of -induction, and that the structural information about its irreducible representations is encoded in the mass matrix . Our analysis sheds further light on the connection between (the classifications of) modular invariants and subfactors, and we will construct and analyze modular invariants from loop group subfactors in a forthcoming publication, including the treatment of all modular invariants.

66 pages, latex, epic, eepic; minor changes, typos fixed, references added

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