Dynamics of supersymmetric SU(nc) and USp(2nc) gauge theories

We study dynamical flavor symmetry breaking in the context of a class of N=1 supersymmetric SU(nc) and USp(2 nc) gauge theories, constructed from the exactly solvable N=2 theories by perturbing them with small adjoint and generic bare hypermultiplet (quark) masses. We find that the flavor U(n(f)) symmetry in SU(n(c)) theories is dynamically broken to U(r) X U(n(f)-r) groups for nf leq nc. In the r=1 case the dynamical symmetry breaking is caused by the condensation of monopoles in the underline(n(f)) representation. For general r, however, the monopoles in the underline(()(n(f))C(r)) representation, whose condensation could explain the flavor symmetry breaking but would produce too-many Nambu--Goldstone multiplets, actually ''break up'' into ''magnetic quarks'' which condense and induce confinement and the symmetry breaking. In USp(2nc) theories with nf leq nc + 1, the flavor SO(2nf) symmetry is dynamically broken to U(nf), but with no description in terms of a weakly coupled local field theory. In both SU(nc) and USp(2 nc) theories, with larger numbers of quark flavors, besides the vacua with these properties, there exist also vacua with no flavor symmetry breaking. (author)