Groupoid Models of $C^*$-algebras and Gelfand Duality

TL;DR

This paper develops a framework for understanding $C^*$-algebras through groupoid models, introducing partial morphisms that extend Gelfand duality and applying this to model complex inductive systems like Jiang-Su and Razak-Jacelon algebras.

Contribution

It introduces partial morphisms of groupoids inducing $*$-morphisms of $C^*$-algebras and extends Gelfand duality to a broader class of morphisms, with applications to important algebraic models.

Findings

Constructed partial morphisms inducing $*$-morphisms of $C^*$-algebras.

Extended Gelfand functor to include partial morphisms.

Modeled inductive systems of Jiang-Su and Razak-Jacelon algebras.

Abstract

We construct a large class of morphisms, which we call partial morphisms, of groupoids that induce $*$-morphisms of maximal and minimal groupoid $C^*$-algebras. We show that the association of a groupoid to its maximal (minimal) groupoid $C^*$-algebra and the association of a partial morphism to its induced morphism are functors (both of which extend the Gelfand functor). We show how to geometrically visualize lots of $*$-morphisms between groupoid $C^*$-algebras. As an application, we construct a groupoid models of the entire inductive systems of the Jiang-Su algebra $\mathcal{Z}$ and the Razak-Jacelon algebra $\mathcal{W}$.