Zero-dimensional compact metrizable spaces as attractors of generalized iterated function systems

Abstract

Miculescu and Mihail in 2008 introduced the concept of a \emph{generalized iterated function system} (GIFS in~short), a particular extension of the classical IFS. The idea is that, instead of families of selfmaps of a metric space~$X$, GIFSs consist of maps defined on a finite Cartesian {$m$-th power} $X^m$ with values in $X$ (in such a case we say that a GIFS is \emph{of order} $m$). It turned out that a great part of the classical {Hutchinson theory} has natural counterpart in this GIFSs' framework. On the other hand, there are known only few examples of~fractal sets which are generated by GIFSs, but which are not IFSs' {attractors}. In the paper we study $0$-dimensional compact metrizable spaces from the perspective of GIFSs' theory. We prove that each such space $X$ (in particular, countable with limit {scattered} height) is homeomorphic to the~attractor of some GIFS on the real line. Moreover, we prove that $X$ can be embedded into the real line $\R$ as {the attractor of some} GIFS of order $m$ and (in the same time) {a nonattractor} of any GIFS of order $m-1$, as well as it can be embedded as {a nonattractor of any GIFS}. {Then} we show that a relatively simple modifications of $X$ deliver spaces whose each connected component is "big" and which are GIFS's { attractors} not homeomorphic with IFS's {attractors}. Finally, we use obtained results to show that a generic compact subset of a Hilbert space is not {the} attractor of any Banach GIFS.