Comments on Orientifolds without Vector Structure

Abstract

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.

34 pages, 3 figures, 1 table

References in corpus (6)

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• Hierarchies from D-brane instantons in globally defined Calabi-Yau Orientifolds
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Cited by in corpus (6)

• GUTs in Type IIB Orientifold Compactifications
• Gauge Threshold Corrections for Local Orientifolds
• (Unoriented) T-folds with few T's
• On the (Non) Perturbative Origin of Quark Masses in D-brane GUT Models
• Orientifolds and D-branes in N=2 gauged linear sigma models
• From Twists and Shifts to L-R asymmetric D-branes