Orientifolding the conifold

In this paper we study the N = 1 supersymmetric field theories realized on the world-volume of type IIB D3-branes sitting at orientifolds of non-orbif old singularities (conifold and generalizations). Several chiral models bel ong to this family of theories. These field theories have a T-dual realizat ion in terms of type IIA configurations of relatively rotated NS fivebranes , D4-branes and orientifold six-planes, with a compact x(6) direction, alon g which the D4-branes have finite extent. Wt compute the spectrum of the D3 -branes directly in the type IIB picture and match the resulting field theo ries with those obtained in the type IIA setup, thus providing non-trivial check of this T-duality. Since the usual techniques to compute the spectrum of the model and check the cancellation of tadpoles cannot he applied to t he case of orientifolds of non-orbifold singularities, we use a different a pproach, and construct the models by partially blowing up orientifolds of C -3/(Z(2) X Z(2)) and C-3/(Z(2) X Z(3)) orbifolds. (C) 2000 Elsevier Science B.V, All rights reserved.