Effective Exponential Drifts on Strata of Abelian Differentials
Siyuan Tang
TL;DR
This work analyzes the $SL_2(\\mathbb{R})$-action on the genus-2 translation-surface stratum $\\mathcal{H}(2)$, establishing an effective exponential-drift phenomenon for upper-triangular dynamics. By combining an effective closing lemma with Margulis-function techniques and leveraging McMullen’s classification alongside Lindenstrauss–Mohammadi–Wang effective equidistribution, the authors show that the discretized transversal dimension along the $P=a_{\\mathbb{R}}u_{\\mathbb{R}}$-orbit is nearly 1; in the genus-2 case, they further deduce the existence of nearby Teichmüller curves with controlled discriminants under certain conditions. The paper develops a comprehensive toolkit—AGY norm, spectral-gap based lattice-point counts, nondivergence estimates, and a Margulis-function framework—to iteratively enhance the dimension of invariance, ultimately connecting dynamics on $\\mathcal{H}_1(2)$ to Teichmüller curves and their arithmetic data. This yields quantitative discreteness results for Teichmüller curves, effective closing lemmas, and density-type statements for unstable foliations, with explicit implications for discriminant bounds and the structure of Weierstrass curves. The results advance the understanding of transverse dynamics in moduli spaces of flat surfaces and provide effective mechanisms to link dynamics with arithmetic geometry via discriminants and Veech groups.
Abstract
We study the dynamics of $SL_{2}(\mathbb{R})$ on the stratum of translation surfaces $\mathcal{H}(2)$. In particular, we prove that an orbit of the upper triangular subgroup of $SL_{2}(\mathbb{R})$ has a discretized dimension of almost $1$ in a direction transverse to the $SL_{2}(\mathbb{R})$-orbit. The proof proceeds via an effective closing lemma, and the Margulis function technique, which serves as an effective version of the exponential drift on $\mathcal{H}(2)$. The idea is based on the use of McMullen's classification theorem, together with Lindenstrauss-Mohammadi-Wang's effective equidistribution theorems in homogeneous dynamics.
