New N=2 superconformal field theories from M/F-theory orbifolds

We consider M-theory on (T-2 x 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 t he probes provide many new examples of N = 2 field theories without Lagrang ian description. All these theories have Coulomb branches, and we find the corresponding Seiberg-Witten curves. The exact solution is encoded in a Hit chin system on an orbifolded torus with punctures. The theories we consider also arise from D3 probes in F-theory on K3 x K3 orbifolds. Interestingly, the relevant F-theory background has frozen Z(n) singularities which are a nalogous 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 l arge-N limit and compute the spectrum of relevant and marginal operators. W e also explain how the decoupling of U(1) factors is manifested in the supe rgravity description. (C) 1999 Elsevier Science B.V.