The torus and the Klein bottle amplitude of permutation orbifolds

The torus and the Klein bottle amplitude coefficients are computed in permutation orbifolds of RCFTʹs in terms of the same quantities in the original theory and the twist group. An explicit expression is presented for the number of self conjugate primaries in the orbifold as a polynomial of the total number of primaries and the number of self conjugate ones in the parent theory. The formulae in the Z2 orbifold illustrate the general results.