Thermodynamic formalism for amenable groups and countable state spaces

TL;DR

This paper develops the thermodynamic formalism for full shifts over countable state spaces on countable amenable groups, establishing pressure, Gibbs measures, and phase transition properties.

Contribution

It introduces pressure, proves existence and properties, and extends Gibbs measure definitions with equivalence results for such systems.

Findings

Existence of pressure with infimum rule

Equivalence of Gibbs measures under regularity conditions

Identification of potentials with unique Gibbs measures at certain temperatures

Abstract

Given the full shift over a countable state space on a countable amenable group, we develop its thermodynamic formalism. First, we introduce the concept of pressure and, using tiling techniques, prove its existence and further properties such as an infimum rule. Next, we extend the definitions of different notions of Gibbs measures and prove their existence and equivalence, given some regularity and normalization criteria on the potential. Finally, we provide a family of potentials that non-trivially satisfy the conditions for having this equivalence and a non-empty range of inverse temperatures where uniqueness holds.