Bound States of Type I' D-particles and Enhanced Gauge Symmetry

Abstract

Duality between the E_8 x E_8 heterotic string and Type I' theory predicts a tower of D(irichlet)-particle bound states corresponding to perturbative heterotic string states. In the limit of infinite Type I' coupling, some of these bound states become massless, giving rise to enhanced E_8 x E_8 gauge symmetry. By taking a different infinite coupling limit, one can recover the E_8 x E_8 gauge bosons of M-theory, compactified on S^1/Z_2. In this paper we use the matrix model description of the D-particle dynamics to study these bound states. We find results consistent with the chain of dualities and clarify a number of issues that arise in the application of the matrix mechanics to this system.