BOUND-STATES OF TYPE I' D-PARTICLES AND ENHANCED GAUGE-SYMMETRY

Duality between the E-8 x E-8 heterotic string and Type I' theory pred icts a tower of D(irichlet)-particle bound states corresponding to per turbative heterotic string states. In the limit of infinite Type I' co upling, some of these bound states become massless, giving rise to enh anced E-8 x E-8 gauge symmetry. By taking a different infinite couplin g limit, one can recover the E-8 x E-8 gauge bosons of M-theory, compa ctified 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 resul ts consistent with the chain of dualities and clarify a number of issu es that arise in the application of the matrix mechanics to this syste m. (C) 1997 Elsevier Science B.V.