Duality Symmetries in Orbifold Models

Abstract

We derive the duality symmetries relevant to moduli dependent gauge coupling constant threshold corrections, in Coxeter ${\bf Z_N}$ orbifolds. We consider those orbifolds for which the point group leaves fixed a 2-dimensional sublattice $\Lambda_2$, of the six dimensional torus lattice $\Lambda_6$, where $\Lambda_6$ cannot be decomposed as $\Lambda_2 \bigoplus{\Lambda_4}.$Comment: 13 pages, QMW--TH--93/21, SUSX--TH--93/1