Symbolic dynamics for the Teichmueller flow
Ursula Hamenstädt
TL;DR
This work develops a symbolic coding for the Teichmüller flow on any component $\mathcal{Q}$ of a stratum of quadratic or abelian differentials by combining train-track technology with a subshift of finite type. A finite-to-one semi-conjugacy from a suspension of a transitive shift to the Teichmüller flow is first established on a dense set, and then extended to a countable-alphabet system to control non-compactness and apply thermodynamic formalism. The paper proves that the $\Phi^t$-invariant Lebesgue measure on $\mathcal{Q}$ is the unique measure of maximal entropy, using Sarig’s theory for countable Markov shifts and prior entropy-maximization results, with implications for the dynamics near the principal boundary of strata. The methodology provides a robust framework for entropy analysis in moduli spaces and sets the stage for potential extensions to affine invariant manifolds and boundary behavior in subsequent work.
Abstract
Let Q be a component of a stratum of abelian or quadratic differentials on an oriented surface of genus $g\geq 0$ with $m\geq 0$ punctures and $3g-3+m\geq 2$. We construct a subshift of finite type $(Ω,σ)$ and a Borel suspension of $(Ω,σ)$ which admits a finite-to-one semi-conjugacy into the Teichmueller flow $Φ^t$ on Q. This is used to show that the $Φ^t$-invariant Lebesgue measure on Q is the unique measure of maximal entropy.
