ACCIDENTAL SYMMETRIES AND N=1 DUALITY IN SUPERSYMMETRIC GAUGE-THEORY

We note that the accidental symmetries which are present in some examp les of duality imply the existence of continuously infinite sets of th eories with the same infrared behavior. These sets interpolate between theories of different flavors and colors; the change in color and fla vor is compensated by interactions (often non-perturbative) induced by operators in the superpotential. As an example we study the behavior of SU(2) gauge theories with 2N(f) doublets; these are dual to SU(N-f- 2) gauge theories whose ultraviolet flavor symmetry is SU(N-f)(L) x SU (N-f)(R) x U(1)(B) but whose flavor symmetry is SU(2N(f)) in the infra red. The infrared SU(2N(f)) flavor symmetry is implemented in the ultr aviolet as a non-trivial transformation on the Lagrangian and matter c ontent of the magnetic theory, involving (generally non-renormalizable ) baryon operators and non-perturbative dynamics. We discuss various i mplications of this fact, including possible new chiral fixed points a nd interesting examples of dangerously irrelevant operators. (C) 1997 Elsevier Science B.V.