N=1 DUALITIES OF SO AND USP GAUGE-THEORIES AND T-DUALITY OF STRING THEORY

Extending recent work on SU gauge theory, we engineer local string mod els for N = 1 four-dimensional SO and USp gauge theories coupled to ma tter in the fundamental. The local models are type IIB orientifolds wi th D7 branes on a curved orientifold 7-plane, and matter realized by a dding D3 branes on the orientifold plane, The Higgs branches of the SO and USp theories can be matched with the moduli spaces of SO and USp instantons on the compact four-dimensional part of the D7 branes world -volume. The R-charge of the gauge theories is identified with a U(1) symmetry on the world-volume of an Euclidean D3 brane instanton. We ar gue that the quantum field theory dualities of these gauge theories ar ise from T-dualities of type IIB strings exchanging D7 and D3 charges. A crucial role is played by the induced D3 charge of D7 branes and an orientifold 7-plane, both partially compactified on a Z(2) orbifold o f K3. (C) 1997 Elsevier Science B.V.