Equicontinuity of the Hutchinson operator $F$ and sensitivity of $F_-$
Aliasghar Sarizadeh
TL;DR
The paper investigates the relationship between equicontinuity of the Hutchinson operator $F$ and sensitivity of the Hutchinson operator $F_-$ for an iterated function system on the circle. It constructs a circle $\mathrm{IFS}$ with an exceptional minimal set and uses a circle map with an attracting fixed point to produce backward-minimal dynamics, yielding equicontinuity of $F$ while $F_-$ remains sensitive. It also presents a concrete non-symmetric example $\mathcal{F}=\{f_1,f_2,f_3,f_4\}$, where $f_1=R_\alpha$ is an irrational rotation and the other maps are piecewise-affine, showing that both $F$ and $F_-$ are equicontinuous on $S^1$. Overall, the results demonstrate that equicontinuity of $F$ does not constrain the sensitivity of $F_-$ and highlight nuanced forward/backward dynamics in circle IFS.
Abstract
For an iterated function system $ \mathcal{F} = \{ f_1, \dots, f_k \} $ of homeomorphisms on a compact metric space $(X, d)$, write $ \mathcal{F}_-= \{ f_1^{-1}, \dots, f_k^{-1} \} $. The objective of this paper is to illustrate an iterated function system $\mathcal{F}$ of homeomorphisms on the circle that the Hutchinson operator of $\mathcal{F}$ is equicontinuous, but the Hutchinson operator of $\mathcal{F}_-$ is sensitive.
