A D=4 N=1 Orbifold of Type I Strings

TL;DR

This paper studies Type I superstring propagation on a specific orbifold with N=1 supersymmetry, revealing the necessity of three sets of D5-branes and exploring spectrum enhancements and superpotential effects.

Contribution

It introduces a detailed analysis of a Z_2xZ_2 orbifold in Type I strings, highlighting the role of D5-branes and superpotential in spectrum consistency.

Findings

Three sets of D5-branes are required for consistency.

Spectrum enhancements occur at 5-brane intersections.

Tree-level superpotential influences Higgsing and brane motions.

Abstract

We consider the propagation of Type I open superstrings on orbifolds with four non-compact dimensions and $N=1$ supersymmetry. In this paper, we concentrate on a non-trivial Z_2xZ_2 example. We show that consistency conditions, arising from tadpole cancellation and algebraic sources, require the existence of three sets of Dirichlet 5-branes. We discuss fully the enhancements of the spectrum when these 5-branes intersect. An amusing attribute of these models is the importance of the tree-level (in Type I language) superpotential to the consistent relationship between Higgsing and the motions of 5-branes.