Effective results on actions of commuting toral automorphisms

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Zhiren Wang, Princeton University

Let G be an abelian subgroup of SL(d,Z). When G acts totally irreducibly on Td the d-dimensional torus, has some hyperbolicity and is not virtually-cyclic, Berend proved that every orbit on Td is either the whole torus or finite. We will discuss effective forms of this theorem and how they are related to number-theoretical problems. This is an analogue of the recent quantitative Furstenberg's theorem concerning the ×2,×3 action on the circle by Bourgain-Lindenstrauss-Michel-Venkatesh.