Open strings on the Neveu-Schwarz 5-brane

We analyze the propagation of open and unoriented strings on the Neveu-Schwarz 5-brane (N5-brane) along the lines of a similar analysis for the SU(2) WZNW models. We discuss the two classes of open descendants of the diagonal models and a series of Z(2) projected models which exist only for even values of the level k and correspond to branes at D-type orbifold singularities. The resulting configurations of branes and planes are T-dual to those relevant to the study of dualities in super Yang-Mills theories, The association of Chan-Paton factors to D-brane multiplicities is possible in the semi-classical limit k --> infinity, but due to strong curvature effects is unclear for finite k, We show that the introduction of a magnetic field implies a twist of the SU(2) current algebra in the open-string sector leading to space-time supersymmetry breaking. (C) 1998 Elsevier Science B.V.