Aspects of Type I Compactifications and Type I-Heterotic Duality

TL;DR

This paper constructs a four-dimensional chiral model from type IIB string theory on a Z-orbifold, explores its dual heterotic model, and discusses the spectrum and duality correspondence.

Contribution

It presents a new chiral four-dimensional model from type IIB on a Z-orbifold and tests its duality with a heterotic model, clarifying spectrum differences.

Findings

The model has gauge group SO(8) × U(12) with three matter generations.

The heterotic dual reproduces the spectrum except for additional twisted states.

Massive states at generic moduli points resolve the spectrum discrepancy.

Abstract

We review the construction of open descendants of the type IIB superstring on the Z-orbifold. It results in a chiral four-dimensional model with gauge group $SO(8) \otimes U(12)$ and three generations of matter in the $(8,12^*)\oplus (1,66)$ representations. As a test of type I - heterotic duality, that reduces to a weak/weak duality in D=4, a heterotic model on the same orbifold is also presented. The massless spectrum reproduces exactly the one found in the type I case apart from additional twisted matter charged with respect to the SO(8) gauge group. The puzzle is solved by noting that at generic points in the moduli space these states get masses.