On string theory on image with mixed 3-form flux: Tree-level S-matrix Original Research Article

We consider superstring theory on image supported by a combination of RR and NSNS 3-form fluxes (with parameter of the NSNS 3-form q). This theory interpolates between the pure RR flux model (image) whose spectrum is expected to be described by a (thermodynamic) Bethe ansatz and the pure NSNS flux model (image) which is described by the supersymmetric extension of the image WZW model. As a first step towards the solution of this integrable theory for generic value of q we compute the corresponding tree-level S-matrix for massive BMN-type excitations. We find that this S-matrix has a surprisingly simple dependence on q: the diagonal amplitudes have exactly the same structure as in the image case but with the BMN dispersion relation image replaced by the one with shifted momentum and mass, image. The off-diagonal amplitudes are then determined from the classical Yang–Baxter equation. We also construct the Pohlmeyer-reduced model corresponding to this superstring theory and find that it depends on q only through the rescaled mass parameter, image, implying that its relativistic S-matrix is q-independent.