D-branes at Singularities, Compactification, and Hypercharge

TL;DR

This paper advances the construction of Standard Model-like gauge theories using D-branes at Calabi-Yau singularities, focusing on topological conditions that isolate hypercharge as the only light U(1) gauge factor.

Contribution

It provides a geometric construction of a compact Calabi-Yau threefold with the necessary topological features for realistic D-brane models, emphasizing hypercharge selection.

Findings

Identified topological conditions for hypercharge isolation

Constructed a compact Calabi-Yau with required properties

Discussed D-instantons' role in symmetry breaking

Abstract

We report on progress towards the construction of SM-like gauge theories on the world-volume of D-branes at a Calabi-Yau singularity. In particular, we work out the topological conditions on the embedding of the singularity inside a compact CY threefold, that select hypercharge as the only light U(1) gauge factor. We apply this insight to the proposed open string realization of the SM of hep-th/0508089, based on a D3-brane at a dP_8 singularity, and present a geometric construction of a compact Calabi-Yau threefold with all the required topological properties. We comment on the relevance of D-instantons to the breaking of global U(1) symmetries.