The duality between the anti-exchange closure operators and the path independent choice operators on a finite set,

A duality between Schrödinger operators on graphs and certain Jacobi matrices.. Annales

tion of disconnectednesses of topological spaces via weak heredity of their regular closure operators, and encompasses the characterization of torsion-free

induced by the class F closed under subgroups, products, and extensions must act discretely on the class F and hence the closure under extensions suffices to obtain

In order to characterize the orthogonal hull of a subcategory of X by means of the orthogonal closure operator, we consider the following. Definition 3.1 An object X

This construction is shown to be symmetric to the first construction in that it gives rise to a natural factorization of the global Galois connection the adjoint part

Let A be an extremal epireflective and co-well powered sub- category of TOP such that [], is compactly productive, weakly hereditary in A. and additive in

In his paper [8] Dunkl defines a commuting set of first order differential- difference operators related to such a G, involving a parameter k E Cm (where m is..

as operators which can be expressed as the product of a generalized scalar A-unitary operator with a regular generalized scalar whose spectrum is contained in the