Heterotic type II string duality and the H monopole problem

Since T duality has been proved only perturbatively and most of the heterotic states map into solitonic, nonperturbative, type II states, the six-dimensional string-string duality between the heterotic string and the type II string is not sufficient for proving the S duality of the former, in terms of the known T duality of the latter. We nevertheless show in detail that the perturbative T duality, together with the heterotic type II duality, does imply the existence of heterotic H monopoles, with the correct multiplicity and multiplet structure. This construction is valid at a generic point in the moduli space of heterotic toroidal compactifications.