Topological Orbit Dimension of MF $C^*$-algebras

TL;DR

This paper explores the topological orbit dimension in MF C*-algebras, establishing its invariance under certain conditions, introducing a new invariant, and linking it to properties like MF-c*-{ extGamma} with implications for algebra classification.

Contribution

It introduces a new invariant $K_{top}^3$, relates existing invariants, and proves their behavior under specific properties in MF C*-algebras, advancing understanding of their structure.

Findings

$K_{top}^2$ is invariant under generating family changes for certain algebras

$K_{top}^3$ vanishes for algebras with property $c^*-{ extGamma}$ and no finite-dimensional representations

The paper defines property MF-c^*-{ extGamma} and links it to the vanishing of $K_{top}^3$

Abstract

This paper is a continuation of our work on D. Voiculescu's topological free entropy dimension in unital C*-algebras. In this paper we first prove the topological free entropy dimension of a MF-nuclear and inner QD algebra is irrelevant to its generating family. Then we give the relation between the topological orbit dimension $K_{top}^2$ and the modified free orbit dimension$ K_2^2$ by using MF-traces. We also introduce a new invariant $K_{top}^3$ which is a modification of the topological orbit dimension $K_{top}^2$ when$ K_{top}^2$ is defined. As the applications of $K_{top}^3$, We prove that$ K_{top}^3(A)=0$ if A has property $ c^*-{\Gamma}$ and has no finite-dimensional representations. We also give the definition of property MF-c^*-{\Gamma}. We then conclude that, for the unital MF $ C^*$-algebra with no finite-dimensional representations, if A has property MF-c*-{\Gamma}, then $K_{top}^3(A)=0$.