Abstract

We show that any real number in [0,1] is a diffusion rate for the wind-tree model with rational parameters. We will also provide a criterion in order to describe the shape of the Lyapunov spectrum of cocycles obtained as suspension of a representation. As an application, we exhibit an infinite family of wind-tree billiards for which the interior of the Lyapunov spectrum is a big as possible: this is the full square (0,1)2. To the best of the knowledge of the authors, these are the first complete description where the interior of the Lyapunov spectrum is known explicitly in dimension two, even for general Fuchsian groups. © 2025 The Author(s)