# D-brane deconstructions in IIB orientifolds

Andres Collinucci (TU Wien)

11.12.2008 at 16:15

Most of the extensively studied IIB orientifold vacua are either toroidal models, or so-called "local" models, where global constraints are neglected. However, tools for analyzing global IIB vacua on non-trivial Calabi-Yau orientifolds are still lacking.
Techniques for systematically treating such setups will be presented in three different pictures: F-theory, IIB D7-brane geometry, and D9-anti-D9 tachyon condensation.
Combining these techniques leads to a resolution of a long-standing mismatch between IIB orientifold D7-brane compactifications on Calabi-Yau threefolds and F-theory on Calabi-Yau fourfolds. We will see that D7-branes in orientifolds generically have singularities, which are at the origin of this apparent mismatch. From F-theory, we will infer the correct formulae for computing charges, geometric moduli space and flux moduli space dimensions in light of the singularities. This will naturally follow from the tachyon condensation picture, which provides a simple framework to treat general D7-brane setups.
Applications of these techniques will be discussed, such as finding F-theory lifts for non-trivial IIB setups.

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