New N=2 superconformal field theories from M/F theory orbifolds
  We consider M-theory on (T^2\times R^2)/Z_n with M5 branes wrapped on R^2. One can probe this background with M5 branes wrapped on T^2. The theories on the probes provide many new examples of N=2 field theories without Lagrangian description. All these theories have Coulomb branches, and we find the corresponding Seiberg-Witten curves. The exact solution is encoded in a Hitchin system on an orbifolded torus with punctures. The theories we consider also arise from D3 probes in F-theory on K3\times K3 orbifolds. Interestingly, the relevant F-theory background has frozen Z_n singularities which are analogous to frozen Z_2 singularities in Type I string theory. We use the F-theory description to find supergravity duals of the probe SCFT's in the large N limit and compute the spectrum of relevant and marginal operators. We also explain how the decoupling of U(1) factors is manifested in the supergravity description. 
Sergei Gukov, Anton Kapustin