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arXiv · 2310.11100

An analogue of a conjecture of Rasmussen and Tamagawa for abelian varieties over function fields

Mentzelos Melistas
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Abstract

Let $L$ be a number field and let $\ell$ be a prime number. Rasmussen and Tamagawa conjectured, in a precise sense, that abelian varieties whose field of definition of the $\ell$-power torsion is both a pro-$\ell$ extension of $L(\mu_\ell)$ and unramified away from $\ell$ are quite rare. In this paper, we formulate an analogue of the Rasmussen--Tamagawa conjecture for non-isotrivial abelian varieties defined over function fields. We provide a proof of our analogue in the case of elliptic curves. In higher dimensions, when the base field is a subfield of the complex numbers, we show that our conjecture is a consequence of the uniform geometric torsion conjecture. Finally, using a theorem of Bakker and Tsimerman we also prove our conjecture unconditionally for abelian varieties with real multiplication.

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Mentzelos Melistas. 2023-10-17. An analogue of a conjecture of Rasmussen and Tamagawa for abelian varieties over function fields. https://arxiv.org/abs/2310.11100

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