Tiling spaces are covering spaces over irrational tori
Darío Alatorre, Diego Rodríguez-Guzmán
TL;DR
This work develops a diffeological framework for one-dimensional tiling spaces and links them to irrational tori. It constructs two fibrational structures over $\mathbb{T}_\alpha$—a Cantor-fiber bundle in the diffeological setting and a flow-based $\mathbb{R}$-principal bundle—using return modules and irrational flows, and leverages the diffeological classification of irrational tori to transfer equivalence notions. The authors prove that strong orbit equivalence of canonical projection tilings corresponds to diffeomorphism of the base irrational tori and to $GL(2,\mathbb{Z})$-conjugacy of the slopes, and they compute $\pi_1(\Omega_\alpha)\cong \mathbb{F}_2$, enabling a structural classification of one-dimensional tiling spaces. Overall, the paper integrates diffeology, tiling theory, and Sturmian dynamics to provide new tools for understanding smooth structures and equivalences in tiling spaces, with potential implications for noncommutative geometry and aperiodic order.
Abstract
We study tiling spaces in the diffeological context. We prove some basic diffeological properties for tiling spaces and analyze two different fiber bundle structures of tiling spaces over irrational tori. We use the diffeological classification of irrational tori which captures their arithmetical escence in order to inherit the diffeological equivalence in the context of one-dimensional tiling spaces.
