Phase transitions for transitive local diffeomorphism with break points on the circle and Holder continuous potentials

TL;DR

The paper studies phase transitions for transitive, non-invertible $C^{1}$-local diffeomorphisms with break points on $\mathbb{S}^{1}$ under Hölder potentials. It proves that an open dense set of continuous potentials yields no phase transitions and preserves a spectral gap for the transfer operator, while potentials with phase transitions exhibit a piecewise analytic pressure and a corresponding spectral behavior with at most two transitions. The authors establish a dense set of potentials for which the transfer operator has a spectral gap for all $t$, derive a complete large deviations framework, and develop a Hofbauer-style multifractal analysis for Birkhoff averages, connecting thermodynamic, probabilistic, and geometric properties. Collectively, these results provide a robust thermodynamic picture for circle maps with break points, clarifying when phase transitions occur and enabling precise large deviations and multifractal descriptions, with implications for the dynamics of non-uniformly expanding systems.

Abstract

It is known that if $f: \mathbb{S}^{1} \rightarrow \mathbb{S}^{1}$ is a transitive $C^{1+α}$-local diffeomorphism non-invertible and non-uniformly expanding, then there is a unique parameter $t_{0} \in (0 , 1]$ such that the topological pressure function $\mathbb{R} \ni t \mapsto P_{top}(f , -t\log|Df|)$ is not analytic, in particular $f$ has a phase transition with respect to potential $φ:= -\log|Df|$. On the other hand, it is known that for continuous potentials, the topological pressure function can exhibit an infinite number of phase transitions. In this paper, we study the possibilities of the behaviour of the topological pressure function and transfer operator for transitive local diffeomorphism with break points on the circle and Hölder continuous potentials. In particular, we showed that: (1) there is an open and dense subset of continuous potentials such that if a Hölder continuous potential belongs to this subset, then it has no phase transition and the transfer operator has the spectral gap property; (2) if a Hölder continuous potential has a phase transition, then the topological pressure function and the associated transfer operator are described. Consequently, every Hölder continuous potential has at most two phase transitions and the set of smooth potentials such that $\mathcal{L}_{f,φ}$ has the spectral gap property, acting on the Hölder continuous space, is dense in the uniform topology. Furthermore, we obtain applications for multifractal analysis of the Birkhoff average.

Theorems & Definitions (51)

• Corollary 1.1: BC21
• Conjecture 1
• Remark 1.2
• Theorem 1.3: BC21
• Theorem 1.4
• Remark 2.1
• Remark 2.2
• Theorem A
• Corollary A
• Theorem B