  Using matrix-model methods we study three different N=2 models: U(N) x U(N)
with matter in the bifundamental representation, U(N) with matter in the
symmetric representation, and U(N) with matter in the antisymmetric
representation. We find that the (singular) cubic Seiberg-Witten curves (and
associated Seiberg-Witten differentials) implied by the matrix models, although
of a different form from the ones previously proposed using M-theory, can be
transformed into the latter and are thus physically equivalent. We also
calculate the one-instanton corrections to the gauge-coupling matrix using the
perturbative expansion of the matrix model. For the U(N) theories with
symmetric or antisymmetric matter we use the modified matrix-model prescription
for the gauge-coupling matrix discussed in ref. [hep-th/0303268]. Moreover, in
the matrix model for the U(N) theory with antisymmetric matter, one is required
to expand around a different vacuum than one would naively have anticipated.
With these modifications of the matrix-model prescription, the results of this
paper are in complete agreement with those of Seiberg-Witten theory obtained
using M-theory methods.
