The Standard Model on a D-brane

TL;DR

This paper embeds the Standard Model on a D3-brane at the non-Abelian orbifold ${\mathbb{C}}^3/\Delta_{27}$, yielding a $N=1$ gauge theory with a rich $U(3)_+ \times U(3)_- \times U(1)^9 / U(1)$ structure. Lepton Yukawas are forbidden by gauge symmetries, but realistic lepton masses can arise from Kähler potential terms after supersymmetry breaking, with a multi-TeV string scale motivating the required suppression and a seesaw–type mechanism for neutrinos. Quark Yukawas appear at tree level, and the low-energy spectrum includes six Higgs doublets and extra weak-scale $U(1)$'s, whose phenomenology—including potential flavor-changing effects and light gauge bosons—merits further study. The framework ties string-scale physics to the Standard Model flavor pattern via spurion-mediated SUSY breaking, offering concrete, testable implications for collider and precision experiments.

Abstract

We present a consistent string theory model which reproduces the Standard Model, consisting of a D3-brane at a simple orbifold singularity. We study some simple features of the phenomenology of the model. We find that the scale of stringy physics must be in the multi-TeV range. There are natural hierarchies in the fermion spectrum and there are several possible experimental signatures of the model.

Figures (1)

• Figure 1: Two views of the quiver diagram of the $\Delta_{27}$ singularity.