Remetrizing dynamical systems to control distances of points in time

Abstract

The main aim of this article is to prove that for any continuous function $f \colon X \to X$, where $X$ is metrizable (or, more generally, for any family $\mathcal{F}$ of such functions, satisfying an additional condition), there exists a compatible metric $d$ on $X$ such that the $n$th iteration of $f$ (more generally, the composition of any $n$ functions from $\mathcal{F}$) is Lipschitz with constant $a_k$ where $(a_k)_{k=1}^{\infty}$ is an arbitrarily fixed sequence of real numbers such that $1 < a_k$ and $\lim\limits_{k\to+\infty}a_k = +\infty$. In particular, any dynamical system can be remetrized in order to significantly control the distance between points by their initial distance.