Eliminating Thurston obstructions and controlling dynamics on curves

Fuente: arXiv
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Main Authors: Bonk, Mario, Hlushchanka, Mikhail, Iseli, Annina
Format: Preprint
Published: 2021
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author Bonk, Mario
Hlushchanka, Mikhail
Iseli, Annina
author_facet Bonk, Mario
Hlushchanka, Mikhail
Iseli, Annina
contents Every Thurston map $f\colon S^2\rightarrow S^2$ on a $2$-sphere $S^2$ induces a pull-back operation on Jordan curves $α\subset S^2\setminus P_f$, where $P_f$ is the postcritical set of $f$. Here the isotopy class $[f^{-1}(α)]$ (relative to $P_f$) only depends on the isotopy class $[α]$. We study this operation for Thurston maps with four postcritical points. In this case a Thurston obstruction for the map $f$ can be seen as a fixed point of the pull-back operation. We show that if a Thurston map $f$ with a hyperbolic orbifold and four postcritical points has a Thurston obstruction, then one can "blow up" suitable arcs in the underlying $2$-sphere and construct a new Thurston map $\widehat f$ for which this obstruction is eliminated. We prove that no other obstruction arises and so $\widehat f$ is realized by a rational map. In particular, this allows for the combinatorial construction of a large class of rational Thurston maps with four postcritical points. We also study the dynamics of the pull-back operation under iteration. We exhibit a subclass of our rational Thurston maps with four postcritical points for which we can give positive answer to the global curve attractor problem.
format Preprint
id arxiv_https___arxiv_org_abs_2105_06938
institution arXiv
publishDate 2021
record_format arxiv
spellingShingle Eliminating Thurston obstructions and controlling dynamics on curves
Bonk, Mario
Hlushchanka, Mikhail
Iseli, Annina
Dynamical Systems
Complex Variables
37F20, 37F10
Every Thurston map $f\colon S^2\rightarrow S^2$ on a $2$-sphere $S^2$ induces a pull-back operation on Jordan curves $α\subset S^2\setminus P_f$, where $P_f$ is the postcritical set of $f$. Here the isotopy class $[f^{-1}(α)]$ (relative to $P_f$) only depends on the isotopy class $[α]$. We study this operation for Thurston maps with four postcritical points. In this case a Thurston obstruction for the map $f$ can be seen as a fixed point of the pull-back operation. We show that if a Thurston map $f$ with a hyperbolic orbifold and four postcritical points has a Thurston obstruction, then one can "blow up" suitable arcs in the underlying $2$-sphere and construct a new Thurston map $\widehat f$ for which this obstruction is eliminated. We prove that no other obstruction arises and so $\widehat f$ is realized by a rational map. In particular, this allows for the combinatorial construction of a large class of rational Thurston maps with four postcritical points. We also study the dynamics of the pull-back operation under iteration. We exhibit a subclass of our rational Thurston maps with four postcritical points for which we can give positive answer to the global curve attractor problem.
title Eliminating Thurston obstructions and controlling dynamics on curves
topic Dynamical Systems
Complex Variables
37F20, 37F10
url https://arxiv.org/abs/2105.06938