Ergodic properties of matrix equilibrium states

TL;DR

This paper investigates the ergodic properties of matrix equilibrium states generated by finite irreducible matrix sets, providing characterizations for entropy, Lyapunov exponents, Bernoulli measures, and mixing conditions.

Contribution

It offers a comprehensive characterization of ergodic properties of matrix equilibrium states based on algebraic properties of the matrices' semigroup, including conditions for zero entropy and Bernoulli measures.

Findings

Characterized when equilibrium states have zero entropy.

Identified conditions for distinct Lyapunov exponents.

Provided criteria for mixing and ergodicity.

Abstract

Given a finite irreducible set of real $d \times d$ matrices $A_1,\ldots,A_M$ and a real parameter $s>0$, there exists a unique shift-invariant equilibrium state associated to $(A_1,\ldots,A_M,s)$. In this article we characterise the ergodic properties of such equilibrium states in terms of the algebraic properties of the semigroup generated by the associated matrices. We completely characterise when the equilibrium state has zero entropy, when it gives distinct Lyapunov exponents to the natural cocycle generated by $A_1,\ldots,A_M$, and when it is a Bernoulli measure. We also give a general sufficient condition for the equilibrium state to be mixing, and give an example where the equilibrium state is ergodic but not totally ergodic. Connections with a class of measures investigated by S. Kusuoka are explored in an appendix.