Approximation by polynomials on quaternionic compact sets

In this paper we obtain several extensions to the quaternionic setting of some results concerning the approximation by polynomials of functions continuous on a compact set and holomorphic in its interior. The results include approximation on compact starlike sets and compact axially symmetric sets. The cases of some concrete particular sets are described in details, including quantitative estimates too

Supersymmetric Toda lattice hierarchies

The origin of the bosonic and fermionic solutions, constructed in [1,2,3], to the symmetry equations corresponding to the two-dimensional bosonic and N=(2|2) supersymmetric Toda lattices is established, and algebras of the corresponding symmetries are derived. The conjecture regarding an N=(2|2) superfield formulation of the N=(2|2) supersymmetric Toda lattice hierarchy, proposed in [16], is proved. The two-dimensional N=(0|2) supersymmetric Toda lattice hierarchy is proposed and its N=(0|2) superfield formulation is discussed. Bosonic and fermionic solutions to the symmetry equation corresponding to the two-dimensional N=(0|2) supersymmetric Toda lattice equation and their algebra are constructed. An infinite class of new two-dimensional supersymmetric Toda-type hierarchies is discussed.Comment: 38 pages LaTeX, to be published in Proceedings of the NATO ARW ``Integrable Hierarchies and Modern Physical Theories'' (Chicago, USA, July 22 - 26, 2000), Kluwer Academic Publisher