Twisted Open Strings from Closed Strings: The WZW Orientation Orbifolds

Abstract

Including {\it world-sheet orientation-reversing automorphisms} ${\hat{h}}_{\sigma }\in H_{-}$ in the orbifold program, we construct the operator algebras and twisted KZ systems of the general WZW {\it orientation orbifold} $A_g(H_{-})/H_{-}$. We find that the orientation-orbifold sectors corresponding to each ${\hat{h}}_{\sigma }\in H_{-}$ are {\it twisted open} WZW strings, whose properties are quite distinct from conventional open-string orientifold sectors. As simple illustrations, we also discuss the classical (high-level) limit of our construction and free-boson examples on abelian $g$.

65 pages, typos corrected