M-Theory Model-Building and Proton Stability

TL;DR

This paper explores how certain string-derived M-theory models can inherently prevent proton decay by utilizing enhanced gauge symmetries, offering a potential solution to proton stability issues in M-theory.

Contribution

It demonstrates that specific heterotic string models with a $Z_2 imes Z_2$ orbifold structure naturally forbid dangerous baryon-decay operators, advancing M-theory model-building.

Findings

Models exhibit an enhanced custodial gauge symmetry.

Proton decay operators are forbidden to all orders.

Geometric interpretation links models to orbifold compactifications.

Abstract

We study the problem of baryon stability in M theory, starting from realistic four-dimensional string models constructed using the free-fermion formulation of the weakly-coupled heterotic string. Suitable variants of these models manifest an enhanced custodial gauge symmetry that forbids to all orders the appearance of dangerous dimension-five baryon-decay operators. We exhibit the underlying geometric (bosonic) interpretation of these models, which have a $Z_2 \times Z_2$ orbifold structure similar, but not identical, to the class of Calabi-Yau threefold compactifications of M and F theory investigated by Voisin and Borcea. A related generalization of their work may provide a solution to the problem of proton stability in M theory.