Z_N x Z_M orientifolds with and without discrete torsion

TL;DR

This paper systematically classifies and constructs four-dimensional Z_N x Z_M orientifolds in type IIB string theory, exploring models with and without discrete torsion, and analyzing their supersymmetry and gauge group properties.

Contribution

It provides a comprehensive classification and explicit construction of Z_N x Z_M orientifolds, including models with discrete torsion and supersymmetry breaking via antibranes.

Findings

Multiple consistent orientifold models identified for various Z_N x Z_M groups.

Discrete torsion reduces the gauge group rank by half.

Supersymmetry can be broken by antibranes in these models.

Abstract

We discuss compact four-dimensional Z_N x Z_M type IIB orientifolds. We take a systematic approach to classify the possible models and construct them explicitely. The supersymmetric orientifolds of this type have already been constructed some time ago. We find that there exist several consistent orientifolds for each of the discrete groups Z_2 x Z_2, Z_2 x Z_4, Z_4 x Z_4, Z_2 x Z_6, Z_2 x Z_6' and Z_6 x Z_6 if anti-D5-branes are introduced. Supersymmetry is broken by the open strings ending on antibranes. The rank of the gauge group is reduced by a factor two if the underlying orbifold space has discrete torsion.