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
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