In this paper we discuss candidate superconformal N = 2 gauge theories that realize the AdS/CFT correspondence with M-theory compactified on the homogeneous Sasakian 7-manifolds M 7 that were classified long ago. In particular we focus on the two cases M 7 = Q 1,1,1 and M 7 = M 1,1,1 , for the latter the Kaluza Klein spectrum being completely known. We show how the toric description of M 7 suggests the gauge group and the supersingleton fields. The conformal dimensions of the latter can be independently calculated by comparison with the mass of baryonic operators that correspond to 5-branes wrapped on supersymmetric 5-cycles and are charged with respect to the Betti multiplets. The entire Kaluza Klein spectrum of short multiplets agrees with these dimensions. Furthermore, the metric cone over the Sasakian manifold is a conifold algebraically embedded in some C p . The ring of chiral primary fields is defined as the coordinate ring of C p modded by the ideal generated by the embedding equations; this ideal has a nice characterization by means of representation theory. The entire Kaluza Klein spectrum is explained in terms of these vanishing relations. We give the superfield interpretation of all short multiplets and we point out the existence of many long multiplets with rational protected dimensions, whose presence and pattern were already noticed in other compactifications and seem to be universal. * Supported in part by EEC under TMR contract ERBFMRX-CT96-0045 and by GNFM.

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Abstract. We generalize to the supersymmetric case the representation of the KP hierarchy as a set of conservation laws for the generating series of the conserved densities. We show that the hierarchy so obtained is isomorphic to the JSKP of Mulase and Rabin. We identify its "bosonic content" with the so-called Darboux-KP hierarchy, which geometrically encompasses the theory of Darboux-Bäcklund transformations, and is an extension both of the KP theory and of the modified KP theory. Finally, we show how the hierarchy can be linearized and how the supersymmetric counterpart of a wide class of rational solution can be quite explicitly worked out.

We show that the geometry of K3 surfaces with singularities of type A-D-E contains enough information to reconstruct a copy of the Lie algebra associated to the given Dynkin diagram. We apply this construction to explain the enhancement of symmetry in F and IIA theories compactified on singular K3's.

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