Natural extensions of unimodal maps: virtual sphere homeomorphisms and prime ends of basin boundaries

Abstract

Let $\{f_t:I\to I\}$ be a family of unimodal maps with topological entropies $h(f_t)>\frac{1}{2}\log 2$, and ${\hat{f}}_t:{\hat{I}}_t\to {\hat{I}}_t$ be their natural extensions, where ${\hat{I}}_t=\underleftarrow{\lim }(I,f_t)$. Subject to some regularity conditions, which are satisfied by tent maps and quadratic maps, we give a complete description of the prime ends of the Barge-Martin embeddings of ${\hat{I}}_t$ into the sphere. We also construct a family $\{{\chi }_t:S^2\to S^2\}$ of sphere homeomorphisms with the property that each ${\chi }_t$ is a factor of ${\hat{f}}_t$, by a semi-conjugacy for which all fibers except one contain at most three points, and for which the exceptional fiber carries no topological entropy: that is, unimodal natural extensions are virtually sphere homeomorphisms. In the case where $\{f_t\}$ is the tent family, we show that ${\chi }_t$ is a generalized pseudo-Anosov map for the dense set of parameters for which $f_t$ is post-critically finite, so that $\{{\chi }_t\}$ is the completion of the unimodal generalized pseudo-Anosov family introduced in [21].

Author accepted manuscript

Cited by in corpus (2)

• Unimodal Measurable Pseudo-Anosov Maps
• Limits of sequences of pseudo-Anosov maps and of hyperbolic 3-manifolds