Open Strings on the Neveu-Schwarz Pentabrane

TL;DR

The paper analyzes open and unoriented strings in the Neveu-Schwarz pentabrane background using open-descendant constructions of rational conformal field theories. It identifies two main classes of models—diagonal A-series descendants and even-k D-type Z2-projected models—whose brane/O-plane configurations relate to dualities in supersymmetric Yang-Mills theories, particularly in the large-$k$ semiclassical limit where CP charges map to D-brane multiplicities. Finite-$k$ curvature complicates brane distinctions and obviates tadpole cancellation, while a boundary magnetic field twists the SU(2) current algebra and breaks spacetime supersymmetry; the framework also accommodates orbifold singularities and T-dualities, offering a path to connect curved-background D-brane dynamics with broader string dualities and potential Calabi-Yau applications.

Abstract

We analyze the propagation of open and unoriented strings on the Neveu-Schwarz pentabrane (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 spacetime supersymmetry breaking.