Three Generations in the Fermionic Construction

TL;DR

This paper constructs three-generation string models with realistic gauge groups using fermionization, revealing models with unique hypercharge normalization and exotic matter content, advancing string phenomenology.

Contribution

It presents the first three-generation models with hypercharge normalization below SU(5) embedding, expanding the landscape of realistic string constructions.

Findings

Models have hypercharge normalization less than SU(5)

All models include fractional charged exotic matter

Models are constructed without relying on Z_2 X Z_2 orbifolds

Abstract

We obtain three generation SU(3)_c X SU(2)_L X U(1)_Y string models in all of the exactly solvable (0,2) constructions sampled by fermionization. None of these examples, including those that are symmetric abelian orbifolds, rely on the Z_2 X Z_2 orbifold underlying the NAHE basis. We present the first known three generation models for which the hypercharge normalization, k_1, takes values smaller than that obtained from an SU(5) embedding, thus lowering the effective gauge coupling unification scale. All of the models contain fractional electrically charged and vectorlike exotic matter that could survive in the light spectrum.