Intersecting Brane Worlds -- A Path to the Standard Model ?
Dieter Lust
TL;DR
The paper surveys intersecting D6-brane world constructions in Type IIA orientifolds as a geometric route to embedding the Standard Model with gravity. It details how SM-like chiral spectra arise from brane intersections, how SUSY can be realized or broken, and how RS consistency conditions (RR/NS tadpole cancellations) guide model building on compact Calabi-Yau spaces. It then analyzes the low-energy actions, including the Born-Infeld-derived scalar potential and gauge couplings with one-loop threshold corrections, and discusses gauge coupling unification and proton decay within this framework. The work highlights both the promise of obtaining SM-like physics from brane intersections and the key open problems, such as achieving fully realistic MSSM-like models, stabilizing moduli with fluxes, and understanding non-perturbative effects and ground-state selection. Overall, it presents a concrete, geometrical approach to string-based SM embedding while outlining major theoretical challenges and directions for future research.
Abstract
In this review we describe the general geometrical framework of brane world constructions in orientifolds of type IIA string theory with D6-branes wrapping 3-cycles in a Calabi-Yau 3-fold. These branes generically intersect in points on the internal space, and the patterns of intersections govern the chiral fermion spectra. We discuss how the open string spectra in intersecting brane models are constructed, how the Standard Model can be embedded, and also how supersymmetry can be realized in this class of string vacua. After the general considerations we specialize the discussion to the case of orbifold backgrounds with intersecting D6-branes and to the quintic Calabi-Yau manifold. Then, we discuss parts of the effective action of intersecting brane world models. Specifically we compute from the Born-Infeld action of the wrapped D-branes the tree-level, D-term scalar potential, which is important for the stability of the considered backgrounds as well as for questions related to supersymmetry breaking. Second, we review the recent computation concerning of gauge coupling unification and also of one-loop gauge threshold corrections in intersecting brane world models. Finally we also discuss some aspects of proton decay in intersecting brane world models.