Non-geometric BPS branes on T-folds

We give a detailed (microscopic) description of the geometric and non-geometric fundamental branes and their bound states in Type II superstring compactifications preserving N = 6 supersymmetry. We consider general boundary states that couple to the twisted sector and compute the relevant annulus amplitudes. We check consistency of the construction by relating the ‘transverse’ channel, corresponding to closed-string ‘tree-level’ exchange, with the ‘direct’ open-string loop channel. Focussing on the Type IIA frame, we show that D0-D4 have the expected tension for a geometric brane, while the non-geometric D2-D6 boundary states have a tension equal to 1/K the one of a geometric brane for the Z_K orbifold. This is consistent with Fricke T-duality of the N = 6 model.