On Gibbs measures for almost additive sequences associated to some relative pressure functions
Yuki Yayama
TL;DR
This paper develops a non-additive thermodynamic formalism for weakly almost additive sequences with bounded variation on subshifts, proving that a bounded Borel hat{f} (and in some cases a continuous hat{f}) can reproduce the asymptotic integrals of log f_n across all invariant measures. It then characterizes the Gibbs-equilibrium structure of hat{f} relative to that of the original sequence, and extends these insights to images of Gibbs measures under one-block factor maps via relative pressure sequences. A key contribution is linking almost additivity of relative pressure sequences to the Gibbs property of factor-map images, with explicit criteria in a special finite-type setting that leverage matrix products and Jordan form analysis. These results illuminate when factor maps preserve (weak) Gibbs properties and provide explicit constructions of the target functions hat{g} or hat{h} governing the image measures. Overall, the work bridges non-additive thermodynamic formalism and symbolic dynamics to yield actionable conditions for the Gibbs behavior of projected or reduced systems.
Abstract
Given a weakly almost additive sequence of continuous functions with bounded variation $\mathcal{F}=\{\log f_n\}_{n=1}^{\infty}$ on a subshift $X$ over finitely many symbols, we study properties of a function $f$ on $X$ such that $\lim_{n\to\infty}\frac{1}{n}\int \log f_n dμ=\int f dμ$ for every invariant measure $μ$ on $X$. Under some conditions we construct a function $f$ on $X$ explicitly and study a relation between the property of $\mathcal{F}$ and some particular types of $f$. As applications we study images of Gibbs measures for continuous functions under one-block factor maps. We investigate a relation between the almost additivity of the sequences associated to relative pressure functions and the fiber-wise sub-positive mixing property of a factor map. For a special type of one-block factor maps between shifts of finite type, we study necessary and sufficient conditions for the image of a one-step Markov measure to be a Gibbs measure for a continuous function.
