Certain free products of graph operator algebras

TL;DR

This paper introduces a new class of graph operator algebras based on edge-colored directed graphs, exploring their structure, $C^*$-envelopes, and properties like simplicity and nuclearity.

Contribution

It develops a framework for generalized Cuntz-Krieger families and analyzes the associated free product $C^*$-algebras with new structural insights.

Findings

Determined $C^*$-envelopes for a broad class of non-selfadjoint algebras

Established connections between graph properties and algebraic properties like simplicity and nuclearity

Investigated the $K$-theory of these free product algebras

Abstract

We develop a notion of a generalized Cuntz-Krieger family of projections and partial isometries where the range of the partial isometries need not have trivial intersection. We associate to these generalized Cuntz-Krieger families a directed graph, with a coloring function on the edge set. We call such a directed graph an edge-colored directed graph. We then study the $C^*$-algebras and the non-selfadjoint operator algebras associated to edge-colored directed graphs. These algebras arise as free products of directed graph algebras with amalgamation. We then determine the $C^*$-envelopes for a large class of the non-selfadjoint algebras. Finally, we relate properties of the edge-colored directed graphs to properties of the associated $C^*$-algebra, including simplicity and nuclearity. Using the free product description of these algebras we investigate the $K$-theory of these algebras.