Embeddings of Relative Dimension Groups for Zero-Dimensional Dynamical Systems

Abstract

Let $π:(X,T)\rightarrow(Y,S)$ be a factor map between zero-dimensional dynamical systems, and let $X_0$ and $Y_0$ be quasi-sections with $π(X_0)=Y_0$. We study the homomorphism $π^*:K^0(Y|Y_0,S)\rightarrow K^0(X|X_0,T)$, $[f]\mapsto[f\circπ]$, between the corresponding relative dimension groups, and identify it with the homomorphism induced by the premorphism between Bratteli--Vershik realizations associated with $π$. Generalizing a result of Glasner and Weiss for minimal Cantor systems, we show that if $Y_0$ is quasi-simple, then $π^*$ is an injective unital order-preserving homomorphism, and that if $X_0=π^{-1}(Y_0)$, then $π^*$ is a unital order embedding; the latter condition is characterized in terms of the premorphism. Examples show that quasi-simplicity cannot be dropped, and that without the condition $X_0=π^{-1}(Y_0)$ the map $π^*$ need not be an order embedding.