String completion of an $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ electroweak model

TL;DR

This paper explores a string theory-based UV completion of the SU(3)_c x SU(3)_L x U(1)_X electroweak model, addressing anomaly cancellation, neutrino mass generation, and baryon number violation within a consistent D-brane framework.

Contribution

It introduces a novel string-inspired approach to unify the 331 model using D-branes and Calabi-Yau singularities, ensuring anomaly freedom and consistent neutrino and baryon number physics.

Findings

The model is free of gauge and string anomalies.

Neutrinos are Dirac particles with light masses from a TeV-scale seesaw.

Baryon number violation via exotic instantons could lead to neutron-antineutron oscillations.

Abstract

The extended electroweak $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X}$ symmetry framework "explaining" the number of fermion families is revisited. While $331$-based schemes can not easily be unified within the conventional field theory sense, we show how to do it within an approach based on D-branes and (un)oriented open strings, on Calabi-Yau singularities. We show how the theory can be UV-completed in a quiver setup, free of gauge and string anomalies. Lepton and baryon numbers are perturbatively conserved, so neutrinos are Dirac-type, and their lightness results from a novel TeV scale seesaw mechanism. Dynamical violation of baryon number by exotic instantons could induce neutron-antineutron oscillations, with proton decay and other dangerous R-parity violating processes strictly forbidden.