Heterotic strings on G_2 orbifolds

TL;DR

This paper investigates heterotic string compactifications on G_2 orbifolds, analyzing gauge symmetry breaking, massless spectra, and comparing results with type II string theories, revealing consistent spectra across different string types.

Contribution

It provides a detailed analysis of heterotic string compactifications on G_2 orbifolds, including gauge group breaking and spectrum computation, with insights into non-standard embeddings and type II comparisons.

Findings

Gauge group breaks to F_4 x E_8 or SO(25)

Massless spectra match reduction from 10D fields

Type IIB and IIA have identical spectra

Abstract

We study compactification of heterotic strings to three dimensions on orbifolds of G_2 holonomy. We consider the standard embedding and show that the gauge group is broken from E_8 x E_8 or SO(32) to F_4 x E_8 or SO(25) respectively. We also compute the spectrum of massless states and compare with the results obtained from reduction of the 10-dimensional fields. Non-standard embeddings are discussed briefly. For type II compactifications we verify that IIB and IIA have equal massless spectrum.