Moduli stabilization from fluxes in a simple IIB orientifold

We study novel type-IIB compactifications on the T⁶/Z₂ orientifold. This geometry arises in the T-dual description of type-I theory on T⁶, and one normally introduces 16 space-filling D3-branes to cancel the RR tadpoles. Here, we cancel the RR tadpoles either partially or fully by turning on three-form flux in the compact geometry. The resulting (super)potential for moduli is calculable. We demonstrate that one can find many examples of = 1 supersymmetric vacua with greatly reduced numbers of moduli in this system. A few examples with >1 supersymmetry or complete supersymmetry breaking are also discussed.