Comments on Orientifolds without Vector Structure
نویسندگان
چکیده
We revisit type I compactifications with a Spin(32)/Z2 gauge bundle that admits no vector structure. We elucidate the relation of this Z2 obstruction to discrete B-field flux and to ’t Hooft flux and clarify some subtleties in the T-duality transformation to type IIA intersecting D-brane models. We reexamine the earliest 3-generation GUT model on magnetized D-branes and show its consistency when a discrete B-flux is switched on. We further generalize partially known results for toroidal models to type I compactifications without vector structure and their mirror dual type IIA orientifolds on genuine Calabi-Yau manifolds. We illustrate this by working out the example of the quintic in some detail. Unité mixte de recherche (UMR 8549) du CNRS et de l’ENS, associée à l’Université Pierre et Marie Curie et aux fédérations de recherche FR684 et FR2687.
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