Katsura-Exel-Pardo self-similar actions, Putnam's binary factors and their limit spaces

TL;DR

This paper links Putnam's dynamical systems from graph embeddings to self-similar groupoid actions, characterizing their limit spaces and dynamics, and providing a planar embedding that addresses a question posed by Putnam.

Contribution

It establishes a connection between Putnam's systems and self-similar groupoid actions, characterizes their limit spaces, and provides a planar embedding answering Putnam's question.

Findings

Limit spaces are bundles of circles and points over a totally disconnected space.

Dynamics on each circle are of the form z→z^n.

A planar embedding of the limit spaces is constructed.

Abstract

We show that the dynamical system associated by Putnam to a pair of graph embeddings is identical to the shift map on the limit space of a self-similar groupoid action on a graph. Moreover, performing a certain out-split on said graph gives rise to a Katsura-Exel-Pardo groupoid action on the out-split graph whose associated limit space dynamical system is conjugate to the previous one. We characterise the self-similar properties of these groupoids in terms of properties of their defining data, two matrices $A$, $B$. We prove a large class of the associated limit spaces are bundles of circles and points which fibre over a totally disconnected space, and the dynamics restricted to each circle is of the form $z\to z^{n}$. Moreover, we find a planar embedding of these spaces, thereby answering a question Putnam posed in his paper.