Ordered ∗-Semigroups and a C∗-Correspondence for a Partial Isometry

Abstract

Certain ∗-semigroups are associated with the universal C∗-algebra generated by a partial isometry, which is itself the universal C∗-algebra of a ∗-semigroup. A fundamental role for a ∗-structure on a semigroup is emphasized, and ordered and matricially ordered ∗-semigroups are introduced, along with their universal C∗-algebras. The universal C∗-algebra generated by a partial isometry is isomorphic to a relative Cuntz-Pimsner C∗-algebra of a C∗-correspondence over the C∗-algebra of a matricially ordered ∗-semigroup. One may view the C∗-algebra of a partial isometry as the crossed product algebra associated with a dynamical system defined by a complete order map modelled by a partial isometry acting on a matricially ordered ∗-semigroup.