FUSION OF TWISTED REPRESENTATIONS

The comultiplication formula for fusion products of untwisted represen tations of the chiral algebra is generalized to include arbitrary twis ted representations. We show that the formulae define a tensor product with suitable properties, and determine the analogue of Zhu's algebra for arbitrary twisted representations. As an example we study the fus ion of representations of the Ramond sector of the N = 1 and N = 2 sup erconformal algebra. In the latter case, certain subtleties arise whic h we describe in detail.