Non-perturbative and flux superpotentials for type I strings on the image orbifold Original Research Article

Non-perturbative effects are studied for type I strings on the image orbifold with Chan–Paton symmetry broken by Wilson lines. Generalizing previous analyses that have focussed on (bi)fundamentals, it is argued that (anti)symmetric representations of the resulting gauge group play a decisive role in generating an ADS-like superpotential in this and related cases. Non-perturbative corrections in the closed string moduli are only allowed if properly dressed with open string fields charged under the anomalous image of the orbifold. A general discussion of instanton effects in SYM and string theories is given. Non-perturbative superpotentials induced by both ED5ʹs and ED1ʹs are analyzed. The superpotential generated by closed string fluxes, viz. Scherk–Schwarz shifts (torsion), R–R 3-form flux as well as non-geometric fluxes is derived. Some preliminary comments on the compatibility of the two kinds of superpotentials and the issue of moduli stabilization are presented.