Asymmetric Orbifolds, Rank Reduction and Heterotic Islands

Abstract

We consider toroidal asymmetric orbifolds of the heterotic string preserving all 16 supercharges, developing a general formalism to study components of the moduli space characterized by rank reduction of the gauge group. In particular we construct six- and four-dimensional heterotic islands with no massless moduli other than the dilaton. The formalism involves the Leech lattice, its automorphisms and their corresponding invariant and normal, or coinvariant, sublattices.

38 pages + appendices; v2: comments added, typos corrected, phase in eq. (3.36) corrected, references updated