Chiral four-dimensional string compactifications with intersecting D-branes

TL;DR

The paper addresses constructing chiral four-dimensional theories from string theory by using Type IIA compactifications with intersecting D6-branes wrapped on 3-cycles. The key approach is to derive the 4d spectrum from intersection numbers $I_{ab}$, ensure RR tadpole and anomaly cancellation, and realize Standard Model-like sectors (including a massless hypercharge) within toroidal and more general Calabi–Yau geometries. It highlights phenomenological features such as Yukawa hierarchies from worldsheet instantons, proton stability from global baryon number, and the possibility of a low string scale in non-supersymmetric setups, while acknowledging core challenges like supersymmetry breaking, NSNS tadpoles, and the need for more explicit Calabi–Yau realizations. The work shows intersecting D6-branes as a compelling brane-world alternative to heterotic constructions, offering concrete mechanisms to generate chiral matter and SM-like gauge groups, and outlines the ongoing research directions to address remaining theoretical and phenomenological issues.

Abstract

We review the construction of chiral four-dimensional compactifications of type IIA string theory with intersecting D6-branes. Such models lead to four-dimensional theories with non-abelian gauge interactions and charged chiral fermions. We discuss the application of these techniques to building of models with spectrum as close as possible to the Standard Model, and review their main phenomenological properties. We also emphasize the advantages/disadvantages of carrying out this idea using supersymmetric of non-supersymmetric models.

Figures (16)

• Figure 1: Picture of heterotic string compactification.
• Figure 2: Fluctuations of string theory around a D$p$-brane configuration are describe as open strings ending on its volume.
• Figure 3: Non-abelian gauge bosons in a configuration of coincident D-branes.
• Figure 4: Picture of D-brane worlds.
• Figure 5: Isolated D-branes at a smooth point in transverse space feel a locally trivial geometry and lead to non-chiral open string spectra.