#### Volume 18, issue 3 (2014)

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The field of definition of affine invariant submanifolds of the moduli space of abelian differentials

### Alex Wright

Geometry & Topology 18 (2014) 1323–1341
##### Abstract

The field of definition of an affine invariant submanifold $\mathsc{ℳ}$ is the smallest subfield of $ℝ$ such that $\mathsc{ℳ}$ can be defined in local period coordinates by linear equations with coefficients in this field. We show that the field of definition is equal to the intersection of the holonomy fields of translation surfaces in $\mathsc{ℳ}$, and is a real number field of degree at most the genus.

We show that the projection of the tangent bundle of $\mathsc{ℳ}$ to absolute cohomology ${H}^{1}$ is simple, and give a direct sum decomposition of ${H}^{1}$ analogous to that given by Möller in the case of Teichmüller curves.

Applications include explicit full measure sets of translation surfaces whose orbit closures are as large as possible, and evidence for finiteness of algebraically primitive Teichmüller curves.

The proofs use recent results of Avila, Eskin, Mirzakhani, Mohammadi and Möller.

##### Keywords
translation surface, abelian differential, $\mathrm{SL}(2,\mathbb{R})$–action, Teichmuller dynamics
##### Mathematical Subject Classification 2010
Primary: 32G15, 37D40