Natural extensions of embeddable semigroup actions

Abstract: Continuous actions of semigroups over a topological space are discussed. We focus on semigroups that can be embedded into a group, and study the problem of defining a "natural extension," that is, defining a corresponding group action by homeomorphisms over an appropriate space that serves as an invertible extension of the original semigroup action. Both feasibility and infeasibility results are shown for surjective continuous semigroup actions, characterizing the existence of such an extension in terms of algebraic properties of the semigroup. We finish by briefly studying topological dynamical properties of the natural extension in the amenable case.