The torus analogue of Mazur's conjecture

From papers

Let SS be an algebraic anisotropic torus defined over Q{\mathbb Q}, let FF be a finitely generated subgroup of S(Q)S({\mathbb Q}), and let Γ\Gamma be any arithmetic subgroup of S(Q)S({\mathbb Q}). Write ΓT=ΓT(Q)\Gamma_T=\Gamma\cap T({\mathbb Q}) for a subtorus TT of SS defined over Q{\mathbb Q}.

The torus analogue of Mazur's conjecture. The connected component of the identity of the closure of the image of FF in Γ\S(R)\Gamma\backslash S({\mathbb R}) equals the connected component of the identity of ΓT\T(R)\Gamma_T\backslash T({\mathbb R}) for some such TT. Equivalently, the closure of the image of FF is dense in the identity component of Γ\S(R)\Gamma\backslash S({\mathbb R}) if and only if every subgroup GG of S(Q)S({\mathbb Q}) surjecting onto the image of FF in Γ\S(R)\Gamma\backslash S({\mathbb R}) is Zariski dense in SS.

This is the paper's central conjecture about closures of finitely generated rational subgroups in compact quotients of anisotropic tori. The source proves it assuming Schanuel's conjecture, while noting that an unconditional proof may follow from more elementary geometry-of-numbers methods.

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Sources & referencesView supporting material

Primary source

Dipendra Prasad, “An analogue of a conjecture of Mazur a question in Diophantine approximation on tori”, arXiv:math/0204359 (2002).

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