ORIENTIFOLDS, BRANES, AND DUALITY OF 4D GAUGE-THEORIES

Recently, a D-brane construction in type IIA string theory was shown t o yield the electric/magnetic duality of four-dimensional N = 1 supers ymmetric U(N-c) gauge theories with N-f flavours of quark. We present here an extension of that construction which yields the electric/magne tic duality for the SO(N-c) and USp(N-c) gauge theories with N-f quark s, by adding an orientifold plane which is consistent with the supersy mmetry. Due to the intersection of the orientifold plane with the NS-N S fivebranes already present, new features arise which are crucial in determining the correct final structure of the dualities. (C) 1997 Els evier Science B.V.