We classify those manifolds mentioned in the title which have nite topological type. Namely we show that any such connected M 4n is isomorphic to a hyperkk ahler quotient of a at quaternionic vector space H d by an abelian group. We also show that a compact connected and simply connected 3-Sasakian manifold of dimension 4n ? 1 whose isometry group has rank n + 1 is isometric to a 3-Sasakian quo...

We study the hyperkk ahler metrics associated to minimal singularities in the nilpotent variety of a semisimple Lie group. We show that Kronheimer's 4-dimensional ALE spaces are naturally realized within the context of coadjoint orbits and can be thought of as certain moduli spaces of SU(2) invariant instantons on R 4 nf0g with appropriate boundary conditions. We also show that the hyperkk ahle...

In this paper, we attempt to investigate the connection between various types of ideals (for examples $(m, n)$-ideal, bi-ideal, interior ideal, quasi ideal, prime ideal and maximal ideal) of an ordered semigroup $(S,cdot ,leq)$ and the correspond hyperideals of its EL-hyperstructure $(S,*)$ (if exists). Moreover, we construct the class of EL-$Gamma$-semihypergroup associated to a partially orde...