Bound states of Type I′ D-particles and enhanced gauge symmetry Original Research Article

Duality between the E8 × E8 heterotic string 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 E8 × E8 gauge symmetry. By taking a different infinite coupling limit, one can recover the E8 × E8 gauge bosons of M-theory, compactified on S1/Z2. 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.