Three Family Models from the Heterotic String

TL;DR

This paper constructs a three-family orbifold GUT model from heterotic string theory with E6 symmetry, highlighting its structure, symmetry breaking, and discussing its flaws such as unmassive exotics and R parity violation.

Contribution

It presents a novel five-dimensional heterotic string-derived three-family orbifold GUT model with specific symmetry breaking patterns and discusses its inherent flaws.

Findings

Model has vector-like exotics with fractional charge, not all acquire mass.

E6 symmetry breaks to Pati-Salam and then to Standard Model.

Identifies flaws that may be addressed with alternative compactifications.

Abstract

In this talk I outline work done in collaboration with R.J. Zhang and T. Kobayashi. We show how to construct the equivalent of three family orbifold GUTs in five dimensions from the heterotic string. I focus on one particular model with E(6) gauge symmetry in 5D, the third family and Higgs doublet coming from the 5D bulk and the first two families living on 4D SO(10) branes. Note the E(6) gauge symmetry is broken to Pati-Salam in 4D which subsequently breaks to the Standard Model gauge symmetry via the Higgs mechanism. The model has two flaws, one fatal and one perhaps only unaesthetic. The model has a small set of vector-like exotics with fractional electromagnetic charge. Unfortunately not all of these states obtain mass at the compactification scale. This flaw is fatal. The second problem is R parity violating interactions. These problems may be avoidable in alternate orbifold compactification schemes. It is these problems which we discuss in this talk.