Moduli space for conifolds as intersection of orthogonal D6 branes

We show that a system of parallel D3 branes near a conifold singularity can be mapped onto an intersecting configuration of orthogonal branes in type IIA string theory. Using this brane configuration, we analyze the Higgs mod uli space of the associated field theory. The dimension of the Higgs moduli space is computed from a geometrical analysis of the conifold singularity. Our results provide evidence for an extended s-rule, In addition, a discre pancy between the prediction of the brane configuration and the result obta ined from a geometrical analysis is noted. This discrepancy can be traced b ack to worldsheet instanton effects. (C) 1999 Published by Elsevier Science B.V. All rights reserved.