Supersymmetry enhancement by monopole operators

We describe a method which allows one to study hidden symmetries in a large class of strongly coupled supersymmetric gauge theories in three dimensions. We apply this method to the ABJM theory and to the infrared limit of =4 SQCD with adjoint and fundamental matter. We show that the U(N) ABJM model with Chern-Simons level k = 1or k = 2 has hidden =8 supersymmetry. Hidden supersymmetry is also shown to occur in =4 d = 3 SQCD with one fundamental and one adjoint hypermultiplet. The latter theory, as well as the U(N) ABJM theory at k = 1, are shown to have a decoupled free sector. This provides evidence that both models are dual to the infrared limit of =8 U(N) super-Yang-Mills theory.