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Discrete Dynamics in Nature and Society
Volume 2011 (2011), Article ID 946913, 23 pages
http://dx.doi.org/10.1155/2011/946913
Research Article

Randomness and Topological Invariants in Pentagonal Tiling Spaces

Facultad de Ciencias, Universidad de Oviedo, 33007 Oviedo, Spain

Received 27 February 2011; Revised 25 April 2011; Accepted 26 April 2011

Academic Editor: Binggen Zhang

Copyright © 2011 Juan García Escudero. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We analyze substitution tiling spaces with fivefold symmetry. In the substitution process, the introduction of randomness can be done by means of two methods which may be combined: composition of inflation rules for a given prototile set and tile rearrangements. The configurational entropy of the random substitution process is computed in the case of prototile subdivision followed by tile rearrangement. When aperiodic tilings are studied from the point of view of dynamical systems, rather than treating a single one, a collection of them is considered. Tiling spaces are defined for deterministic substitutions, which can be seen as the set of tilings that locally look like translates of a given tiling. Čech cohomology groups are the simplest topological invariants of such spaces. The cohomologies of two deterministic pentagonal tiling spaces are studied.