Boundary quotient C*‐algebras of semigroups

On Countable Completions of Quotient Ordered Semigroups

A poset is said to be ω-chain complete if every countable chain in it has a least upper bound. It is known that every partially ordered set has a natural ω-completion. In this paper we study the ω-completion of partially ordered semigroups, and the topological action of such a semigroup on its ω-completion. We show that, for partially ordered semigroups, ω-completion and quotient with respect t...

Semigroups of Impedance Conservative Boundary Control Systems

The external Cayley transform is used for the conversion of linear dynamical systems between scattering and impedance forms. We study this transform in the formal setting of colligations which includes all impedance (energy) conservative boundary control systems. Practically motivated sufficient conditions are given to describe when such colligations have well-defined semigroups. We apply these...

Absorption semigroups and dirichlet boundary conditions

compactifications and representations of transformation semigroups

this thesis deals essentially (but not from all aspects) with the extension of the notion of semigroup compactification and the construction of a general theory of semitopological nonaffine (affine) transformation semigroup compactifications. it determines those compactification which are universal with respect to some algebric or topological properties. as an application of the theory, it is i...

Notions of Size and Combinatorial Properties of Quotient Sets in Semigroups

An IP* set in a semigroup is one which must intersect the set of finite products from any specified sequence. (If the semigroup is noncommutative, one must specify the order of the products, resulting in “left” and “right” IP* sets.) If A is a subset of N with positive upper density, then the difference set A−A = {x ∈ N : there exists y ∈ A with x+ y ∈ A} is an IP* set in (N,+). Defining analog...