M-Theory and Hypercharge
N. D. Lambert, P. C. West
TL;DR
The paper explores the possibility that the electro-weak and strong interactions originate from M-theory brane dynamics, focusing on configurations where an M-fivebrane wrapped on a Riemann surface yields a low-energy action corresponding to a non-Abelian gauge theory with a nontrivial $U(1)$ factor. It demonstrates how hypercharge can arise from the brane setup, deriving a $U_R(1)$ charge ${\frac{1}{N_1}-\frac{1}{N_2}}$ and a decoupled $U_C(1)$, and presents a toy non-chiral model with $SU(2)\times SU(3)$ and a $(\mathbf{2},\mathbf{3})$ hypermultiplet carrying hypercharge $\pm 1/6$. By analyzing the IIA limit (NS5–D4 brane system) and the low-energy effective action on the M-fivebrane, the authors connect brane moduli to physical states, including neutrino-like zero modes and solitonic states corresponding to charged particles. Although not yet yielding a fully realistic Standard Model, the framework offers a finite, string-theoretic route to unification and highlights key issues—chirality, SUSY breaking, and confinement—that must be addressed to achieve a viable brane-based description of fundamental interactions.
Abstract
We discuss the possibility that the electro-weak and strong interactions arise as the low energy effective description of branes in M-theory. As a step towards constructing such a model we show how one can naturally obtain SU(N_1)\times SU(N_2)\times U(1) gauge theories from branes, including matter in the bi-fundamental representation of SU(N_1)\times SU(N_2) which are fractionally charged under U(1).