Finite level geometry of fractional branes

Abstract

In some CFT models of simple current type, which are used to describe string theory on orbifolds and (adjoint) cosets of Lie groups, there arise fixed points of the simple current group. In these cases, the standard procedure to associate functions to Ishibashi states by averaging out the action of the simple current group, gives functions with unsatisfactory properties. In some cases the averaged Ishibashi function simply vanishes, which we see explicitly in SO(3) at level k=4l+2. In this note, an alternative function assignment is suggested, and it is shown that in some cases the resulting Ishibashi functions are orthogonal.