On the thin boundary of the fat attractor

Abstract

For, $0<\lambda <1$, consider the transformation $T(x)=dx$ (mod 1) on the circle $S^1$, a $C^1$ function $A:S^1\to \mathbb{R}$, and, the map $F(x,s)=(T(x),\lambda s+A(x))$, $(x,s)\in S^1\times \mathbb{R}$. We denote $\mathcal{B}={\mathcal{B}}_{\lambda }$ the upper boundary of the attractor (known as fat attractor). We are interested in the regularity of ${\mathcal{B}}_{\lambda }$, and, also in what happens in the limit when $\lambda \to 1$. We also address the analysis of the following conjecture which were proposed by R. Bamón, J. Kiwi, J. Rivera-Letelier and R. Urzúa: for any fixed $\lambda$, $C^1$ generically on the potential $A$, the upper boundary ${\mathcal{B}}_{\lambda }$ is formed by a finite number of pieces of smooth unstable manifolds of periodic orbits for $F$. We show the proof of the conjecture for the class of $C^2$ potentials $A(x)$ satisfying the twist condition (plus a combinatorial condition). We do not need the generic hypothesis for this result. We present explicit examples. On the other hand, when $\lambda$ is close to $1$ and the potential $A$ is generic a more precise description can be done. In this case the finite number of pieces of $C^1$ curves on the boundary have some special properties. Having a finite number of pieces on this boundary is an important issue in a problem related to semi-classical limits and micro-support. This was consider in a recent published work by A. Lopes and J. Mohr. Finally, we present the general analysis of the case where $A$ is Lipschitz and its relation with Ergodic Transport