Lattice Realizations of the Open Descendants of Twisted Boundary Conditions for sl(2) A-D-E Models

Abstract

The twisted boundary conditions and associated partition functions of the conformal sl(2) A-D-E models are studied on the Klein bottle and the M\"obius strip. The A-D-E minimal lattice models give realization to the complete classification of the open descendants of the sl(2) minimal theories. We construct the transfer matrices of these lattice models that are consistent with non-orientable geometries. In particular, we show that in order to realize all the Klein bottle amplitudes of different crosscap states, not only the topological flip on the lattice but also the involution in the spin configuration space must be taken into account. This involution is the $Z_2$ symmetry of the Dynkin diagrams which corresponds to the simple current of the Ocneanu algebra.