Permutation Orientifolds
  We consider orientifold actions involving the permutation of two identical factor theories. The corresponding crosscap states are constructed in rational conformal field theory. We study group manifolds, in particular the examples $SU(2) \times SU(2)$ and $U(1)\times U(1)$ in detail, comparing conformal field theory results with geometry. We then consider orientifolds of tensor products of N=2 minimal models, which have a description as coset theories in rational conformal field theory and as Landau Ginzburg models. In the Landau Ginzburg language, B-orientifolds and D-branes are described in terms of matrix factorizations of the superpotential. We match the factorizations with the corresponding crosscap states. 
Ilka Brunner and Vladimir Mitev