The General Twisted Open WZW String
  We recently studied two large but disjoint classes of twisted open WZW strings: the open-string sectors of the WZW orientation orbifolds and the so-called basic class of twisted open WZW strings. In this paper, we discuss {\it all T-dualizations} of the basic class to construct the {\it general} twisted open WZW string -- which includes the disjoint classes above as special cases. For the general case, we give the {\it branes} and {\it twisted non-commutative geometry} at the classical level and the {\it twisted open-string KZ equations} at the operator level. Many examples of the general construction are discussed, including in particular the simple case of twisted free-bosonic open strings. We also revisit the open-string sectors of the general WZW orientation orbifold in further detail. For completeness, we finally review the {\it general twisted boundary state equation} which provides a complementary description of the general twisted open WZW string. 
M.B. Halpern and C. Helfgott