Moduli Space of CHL Strings

TL;DR

This paper explores a specific orbifold of heterotic string theory that reduces the moduli space dimension while maintaining supersymmetry, revealing new symmetry points and supporting S-duality in four dimensions.

Contribution

It introduces a new orbifold construction of heterotic strings that results in a reduced moduli space with preserved supersymmetry and demonstrates invariance under electric-magnetic duality in D=4.

Findings

Identification of non-simply-laced enhanced symmetry points

Invariance of gauge groups under duality in D=4

Construction of moduli space for reduced rank theories

Abstract

We discuss an orbifold of the toroidally compactified heterotic string which gives a global reduction of the dimension of the moduli space while preserving the supersymmetry. This construction yields the moduli space of the first of a series of reduced rank theories with maximal supersymmetry discovered recently by Chaudhuri, Hockney, and Lykken. Such moduli spaces contain non-simply-laced enhanced symmetry points in any spacetime dimension D<10. Precisely in D=4 the set of allowed gauge groups is invariant under electric-magnetic duality, providing further evidence for S-duality of the D=4 heterotic string.