Magnetic Flux in Toroidal Type I Compactification

TL;DR

This work analyzes Type I string theory compactified on tori with magnetic flux on D9-branes, showing that such flux enforces a noncommutative deformation of open-string coordinates and can yield chiral fermions and engineered gauge-group ranks. By employing boundary-state techniques and computing one-loop amplitudes, the authors derive RR-tadpole cancellation conditions that reveal induced D5-brane charges and a framework in which the gauge group can be reduced via flux quanta and brane configurations. They demonstrate that fluxed D9-branes support unitary gauge factors, generate chiral spectra in open-string sectors, and inherently break supersymmetry, though NSNS tadpoles and open-string tachyons pose stability challenges. The paper also ties the flux construction to T-dual descriptions with branes at angles and discusses a concrete four-generation example, illustrating both the potential and the obstacles for phenomenological model-building within this setup.

Abstract

We discuss the compactification of type I strings on a torus with additional background gauge flux on the D9-branes. The solutions to the cancellation of the RR tadpoles display various phenomenologically attractive features: supersymmetry breaking, chiral fermions and the opportunity to reduce the rank of the gauge group as desired. We also point out the equivalence of the concept of various different background fields and noncommutative deformations of the geometry on the individual D9-branes by constructing the relevant boundary states to describe such objects.

Figures (3)

• Figure 1: T-duality of D-branes with flux
• Figure 2: Open string sectors
• Figure 3: The four generation D-brane setting