Semicontinuity of dimension and measure for locally scaling fractals

L. B. Jonker¹ ; J. J. P. Veerman²

¹ Queen's University Kingston, Ontario, Canada
² Department of Mathematical Sciences Portland State University Portland, OR 97207, U.S.A.

Fundamenta Mathematicae, Tome 173 (2002) no. 2, pp. 113-131

Résumé

The basic question of this paper is: If you consider two iterated function systems close to each other in an appropriate topology, are the dimensions of their respective invariant sets close to each other? It is well known that the Hausdorff dimension (and Lebesgue measure) of the invariant set does not depend continuously on the iterated function system. Our main result is that (with a restriction on the “non-conformality” of the transformations) the Hausdorff dimension is a lower semicontinuous function in the $C^1$-topology of the transformations of the iterated function system. The same question is raised of the Lebesgue measure of the invariant set. Here we show that it is an upper semicontinuous function of the transformations. We also include some corollaries of these results, such as the equality of box and Hausdorff dimensions in these cases.

Détail

DOI : 10.4064/fm173-2-2

Keywords: basic question paper you consider iterated function systems close each other appropriate topology dimensions their respective invariant sets close each other known hausdorff dimension lebesgue measure invariant set does depend continuously iterated function system main result restriction non conformality transformations hausdorff dimension lower semicontinuous function topology transformations iterated function system question raised lebesgue measure invariant set here upper semicontinuous function transformations include corollaries these results equality box hausdorff dimensions these cases