Comments on Gepner Models and Type I Vacua in String Theory

TL;DR

This paper constructs open string models based on Gepner models, focusing on six-dimensional cases, revealing diverse symmetry breaking patterns and connecting various models through Klein-bottle projections.

Contribution

It introduces new open descendants of Gepner models in six dimensions and relates models without open sectors to Klein-bottle projections.

Findings

Rich patterns of Chan-Paton symmetry breaking

Various numbers of tensor multiplets, including zero

Connection between models with and without open sectors

Abstract

We construct open descendants of Gepner models, concentrating mainly on the six-dimensional case, where they give type I vacua with rich patterns of Chan-Paton symmetry breaking and various numbers of tensor multiplets, including zero. We also relate the models in $D < 10$ without open sectors, recently found by other authors, to the generalized Klein-bottle projections allowed by the crosscap constraint.