English

Rauzy induction of polygon partitions and toral $\mathbb{Z}^2$-rotations

Dynamical Systems 2021-12-02 v6 Metric Geometry

Abstract

We extend the notion of Rauzy induction of interval exchange transformations to the case of toral Z2\mathbb{Z}^2-rotation, i.e., Z2\mathbb{Z}^2-action defined by rotations on a 2-torus. If XP,R\mathcal{X}_{\mathcal{P},R} denotes the symbolic dynamical system corresponding to a partition P\mathcal{P} and Z2\mathbb{Z}^2-action RR such that RR is Cartesian on a sub-domain WW, we express the 2-dimensional configurations in XP,R\mathcal{X}_{\mathcal{P},R} as the image under a 22-dimensional morphism (up to a shift) of a configuration in XP^W,R^W\mathcal{X}_{\widehat{\mathcal{P}}|_W,\widehat{R}|_W} where P^W\widehat{\mathcal{P}}|_W is the induced partition and R^W\widehat{R}|_W is the induced Z2\mathbb{Z}^2-action on WW. We focus on one example XP0,R0\mathcal{X}_{\mathcal{P}_0,R_0} for which we obtain an eventually periodic sequence of 2-dimensional morphisms. We prove that it is the same as the substitutive structure of the minimal subshift X0X_0 of the Jeandel-Rao Wang shift computed in an earlier work by the author. As a consequence, P0\mathcal{P}_0 is a Markov partition for the associated toral Z2\mathbb{Z}^2-rotation R0R_0. It also implies that the subshift X0X_0 is uniquely ergodic and is isomorphic to the toral Z2\mathbb{Z}^2-rotation R0R_0 which can be seen as a generalization for 2-dimensional subshifts of the relation between Sturmian sequences and irrational rotations on a circle. Batteries included: the algorithms and code to reproduce the proofs are provided.

Keywords

Cite

@article{arxiv.1906.01104,
  title  = {Rauzy induction of polygon partitions and toral $\mathbb{Z}^2$-rotations},
  author = {Sébastien Labbé},
  journal= {arXiv preprint arXiv:1906.01104},
  year   = {2021}
}

Comments

v1:36 p, 11 fig; v2:40 p, 12 fig, rewritten before submission; v3:after reviews; v4:typos and updated references; v5:typos and abstract; v6: added a paragraph commenting that Algo 1 may not halt. Jupyter notebook available at https://nbviewer.jupyter.org/url/www.slabbe.org/Publications/arXiv_1906_01104.ipynb