Magnetized four-dimensional Z2×Z2 orientifolds Original Research Article

We study deformations of Z2×Z2 (shift-)orientifolds in four dimensions in the presence of both uniform Abelian internal magnetic fields and quantized NS–NS Bab backgrounds, that are shown to be equivalent to asymmetric shift-orbifold projections. These models are related by T-duality to orientifolds with D-branes intersecting at angles. As in corresponding six-dimensional examples, D9-branes magnetized along two internal directions acquire a charge with respect to the R–R six-form, contributing to the tadpole of the orthogonal D5-branes (“brane transmutation”). The resulting models exhibit rank reduction of the gauge group and multiple matter families, due both to the quantized Bab and to the background magnetic fields. Moreover, the low-energy spectra are chiral and anomaly free if additional D5-branes longitudinal to the magnetized directions are present, and if there are no Ramond–Ramond tadpoles in the corresponding twisted sectors of the undeformed models.