Abstract: 
We consider a new largeN limit, in which the 't Hooft coupling grows with N. We argue that a class of largeN equivalences, which is known to hold in the 't Hooft limit, can be extended to this very strongly coupled limit. Hence this limit may lead to a new way of studying corrections to the 't Hooft limit, while keeping nice properties of the latter. As a concrete example, we describe largeN equivalences between the ABJM theory and its orientifold projection. The quivalence implies that operators neutral under the projection symmetry have the same correlation functions in two theories at largeN. Usual field theory arguments are valid when 't Hooft coupling \lambda\sim N/k is fixed and observables can be computed by using a planar diagrammatic expansion. With the help of the AdS/CFT correspondence, we argue that the equivalence extends to stronger coupling regions, N >> k, including the Mtheory region N >> k^5. In the second part of the talk, we pursue the equivalence between supersymmetric ChernSimonsmatter theories and consider the other orbifold equivalence between quiver ChernSimons matter theories including flavors which have gravity duals.
