THE SO(32) HETEROTIC STRING ON A K3 SURFACE

The SO(32) heterotic string on a K3 surface is analyzed in terms of th e dual theory of a type II string (or F-theory) on an elliptically fib red Calabi-Yau manifold. The results are in beautiful agreement with e arlier work by Witten using very different methods. In particular, we find gauge groups of SO(32) x Sp(k) appearing at points in the moduli space identified with point-like instantons and see hypermultiplets in the (32, 2k) representation becoming massless at the same time. We al so discuss some aspects of the E(8) X E(8) case.