M Theory Fivebrane Interpretation for Strong Coupling Dynamics of SO(N_c) Gauge Theories

We study M theory fivebranes to understand the moduli space of vacua of N=1 supersymmetric SO(N_c) gauge theory with N_f flavors in four dimensions. We discuss how the various branches of this theory arise in the string/M theory brane configurations and compare our results with the ones obtained earlier by Intriligator and Seiberg in the context of field theory. In the M theory approach, we explain the various branches from the asymptotic position of semi-infinite D4 branes in the $w=x^8+i x^9$ direction, which is closely related to the eigenvalues of the meson matrix $M^{ij} = Q^{i}_a Q^{j}_a$ where $Q^{i}_a$ is a squark multiplet ( $i=1, \cdots, 2N_f$ and $a=1, \cdots, N_c$).In M theory, these branches are explained by observing a new phenomena which did not occur for the gauge groups SU(N_c) or Sp(N_c).