On string models with Scherk-Schwarz supersymmetry breaking

TL;DR

This paper develops a broad class of four-dimensional string models with Scherk-Schwarz supersymmetry breaking using freely acting orbifolds, exploring their properties, stability, and specific examples like a Z_3 x Z_3' heterotic model.

Contribution

It introduces a new framework for constructing chiral string models with Scherk-Schwarz supersymmetry breaking via combined orbifold projections, analyzing their stability and supersymmetry properties.

Findings

Tachyons are absent or limited in certain moduli space regions.

Several new models with orthogonal supersymmetries at different fixed points are found.

A detailed Z_3 x Z_3' heterotic example is presented.

Abstract

We construct a general class of chiral four-dimensional string models with Scherk--Schwarz supersymmetry breaking, involving freely acting orbifolds. The basic ingredient is to combine an ordinary supersymmetry-preserving Z_N projection with a supersymmetry-breaking projection Z_M' acting freely on a subspace of the internal manifold. A crucial condition is that any generator of the full orbifold group Z_N x Z_M' must either preserve some supersymmetry or act freely in order to become irrelevant in some large volume limit. Tachyons are found to be absent or limited to a given region of the tree-level moduli space. We find several new models with orthogonal supersymmetries preserved at distinct fixed-points. Particular attention is devoted to an interesting Z_3 x Z_3' heterotic example.