Freezing phase transition for the Thue-Morse subshift

TL;DR

This paper investigates a freezing phase transition in the pressure function associated with the Thue-Morse subshift, showing that for large enough parameters, the pressure becomes zero, extending and clarifying previous results.

Contribution

The paper rigorously proves the existence of a freezing phase transition for the Thue-Morse subshift's potential, addressing gaps in earlier proofs and providing a clearer analysis.

Findings

Pressure function equals zero for large 2

Freezing phase transition occurs in the system

Clarifies previous incomplete proofs

Abstract

On the full shift on two symbols, we consider the potential defined by $V(x) = \frac{1}{n}$ where $n$ denotes the longest common prefix between the infinite word $x$ and an element of the subshift associated to the Thue-Morse substitution. Given a non negative real number $\beta$, the pressure function is $P(\beta):=\sup\left\{h_{\mu}+\beta\int V\,d\mu\right\},$ where the supremum is taken over all shift invariant probabilities $\mu$ on the full shift and $h_{\mu}$ is the Kolmogorov entropy. We prove that there is a freezing phase transition for the potential $V$: For $\beta$ large enough, the pressure $P(\be)$ is equal to zero. Similar results were previously published by Bruin and Leplaideur in \cite{BL2}, \cite{Bruin-Leplaid-13} but their proofs contained significant gaps and required substantial clarification.