Three-Way Tiling Sets in Two Dimensions

In this article we show that there exist measurable sets W⊂ℝ² with finite measure that tile ℝ² in a measurable way under the action of a expansive matrix A, an affine Weyl group [(W)tilde]widetilde{W} , and a full rank lattice [varGammatilde] ì mathbbR²widetilde{varGamma}subsetmathbb{R}^{2} . This note is follow-up research to the earlier article “Coxeter groups and wavelet sets” by the first and second authors, and is also relevant to the earlier article “Coxeter groups, wavelets, multiresolution and sampling” by M. Dobrescu and the third author. After writing these two articles, the three authors participated in a workshop at the Banff Center on “Operator methods in fractal analysis, wavelets and dynamical systems,” December 2–7, 2006, organized by O. Bratteli, P. Jorgensen, D. Kribs, G. ólafsson, and S. Silvestrov, and discussed the interrelationships and differences between the articles, and worked on two open problems posed in the Larson-Massopust article. We solved part of Problem 2, including a surprising positive solution to a conjecture that was raised, and we present our results in this article.