Exact Standard Model Structures from Intersecting Branes

Abstract

I discuss two types of non-supersymmetric string model constructions that give at low energy exactly the Standard model (SM) with no additional matter/and or gauge group factors. The construction is based on D6 branes intersecting at angles in a compactification of type IIA theory on a decomposable orientifolded $T^6$ torus. The first type is based on five and six stack SM-like constructions at the string scale while, the other construction is based on a four stack GUT left-right symmetric structure centered around the Pati-Salam $SU(4)_C \times SU(2)_L \times SU(2)_R$ gauge group. All classes of models exbibit important phenomenological properties including a stable proton and sizes of neutrino masses in consistency with neutrino oscillation experiments. The models are non-SUSY, but amazingly, they allow the existence of supersymmetric particles!