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arXiv · 2609.33792

Rank stability of elliptic curves over $\mathbb{F}_q(t)$ in residue classes

Steve Fan·Sun Woo Park
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Abstract

Fix a prime $\ell$. Let $K = \mathbb{F}_q(t)$ be a global function field such that $\gcd(q,6) = 1$ and $q \equiv 1 \pmod \ell$. Let $E$ be a non-isotrivial elliptic curve over $K$. Given a fixed monic polynomial $Q$ over $\mathbb{F}_q$, and assuming some mild conditions on $E$, we show that the rank of $E$ does not change with respect to a positive proportion of $\mathbb{Z}/\ell \mathbb{Z}$ extensions $K(\sqrt[\ell]{f})/K$, as $f$ varies over the set of monic polynomials over $\mathbb{F}_q$ such that $f \equiv A \pmod Q$ for any given polynomial $A$. We obtain this result by combining analytic and probabilistic techniques to study the distribution of certain prime Selmer groups of auxiliary abelian varieties constructed from these polynomials $f$.

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Steve Fan, Sun Woo Park. 2026-09-27. Rank stability of elliptic curves over $\mathbb{F}_q(t)$ in residue classes. https://arxiv.org/abs/2609.33792

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