Thermodynamic formalism of interval maps for upper semi-continuous potentials: Makarov-Smirnov's formalism

TL;DR

This paper extends thermodynamic formalism to interval maps with upper semi-continuous potentials, providing explicit characterizations of pressure functions and developing a real analogue of Makarnov-Smirnov's formalism.

Contribution

It introduces a new formalism for upper semi-continuous potentials, generalizes existing results for H"older and geometric potentials, and simplifies proofs of Makarnov-Smirnov's formalism.

Findings

Explicit characterization of pressure functions for negative t

Recovery of known results for H"older potentials

Development of a real version of Makarnov-Smirnov's formalism

Abstract

In this paper, we study the thermodynamic formalism of interval maps $f$ with sufficient regularity, for a sub class $\mathcal{U}$ composed of upper semi-continuous potentials which includes both H\"{o}lder and geometric potentials. We show that for a given $u\in \mathcal{U}$ and negative values of $t$, the pressure function $P(f,-tu)$ can be calculated in terms of the corresponding hidden pressure function $\widetilde{P}(f,-tu)$. Determination of the values $t\in(-\infty,0)$ at which $P(f,-tu)\neq \widetilde{P}(f,-tu)$ is also characterized explicitly. When restricting to the H\"{o}lder continuous potentials, our result recovers Theorem B in [Li \& Rivera-Letelier 2013] for maps with non-flat critical points. While restricting to the geometric potentials, we develop a real version of Makarnov-Smirnov's formalism, in parallel to the complex version shown in [Makarnov \& Smirnov 2000, Theo A,B]. Moreover, our results also provide a new and simpler proof (using [Ruelle 1992, Coro6.3]) of the original Makarnov-Smirnov's formalism in the complex setting, under an additional assumption about non-exceptionality, i.e., [Makarnov \& Smirnov 2000, Theo 3.1].