First-order definability of Campana Points and Darmon Points in algebraic function fields in one variable over number fields

Fuente: arXiv
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Autor principal: De Rasis, Juan Pablo
Formato: Preprint
Publicado: 2025
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author De Rasis, Juan Pablo
author_facet De Rasis, Juan Pablo
contents We give first-order definitions of Campana and Darmon points in algebraic function fields in one variable over number fields. These sets are geometric generalizations of $n$-full integers (integers whose nonzero valuations are at least $n$) and perfect $n$th powers, respectively, to more general algebraic varieties. For this we exploit the theory of quadratic Pfister forms, which were used by Becher, Daans & Dittmann to extend to the case of algebraic function fields in one variable the methods used by Koenigsmann when proving that $\mathbb{Z}$ is universally defined in $\mathbb{Q}$. These methods had already been generalized to arbitrary global fields by Park (2013) and Eisenträger & Morrison (2018), and the author had already exploited these methods to find first-order definitions of Campana points (2024) and Darmon points (2024, with Handley) in the context of number fields. With the newly expanded version of these methods, we now transfer those results to the new context of algebraic function fields in one variable over number fields.
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spellingShingle First-order definability of Campana Points and Darmon Points in algebraic function fields in one variable over number fields
De Rasis, Juan Pablo
Number Theory
Algebraic Geometry
Logic
11U05 (Primary), 11E81, 12L05, 12F20 (secondary)
We give first-order definitions of Campana and Darmon points in algebraic function fields in one variable over number fields. These sets are geometric generalizations of $n$-full integers (integers whose nonzero valuations are at least $n$) and perfect $n$th powers, respectively, to more general algebraic varieties. For this we exploit the theory of quadratic Pfister forms, which were used by Becher, Daans & Dittmann to extend to the case of algebraic function fields in one variable the methods used by Koenigsmann when proving that $\mathbb{Z}$ is universally defined in $\mathbb{Q}$. These methods had already been generalized to arbitrary global fields by Park (2013) and Eisenträger & Morrison (2018), and the author had already exploited these methods to find first-order definitions of Campana points (2024) and Darmon points (2024, with Handley) in the context of number fields. With the newly expanded version of these methods, we now transfer those results to the new context of algebraic function fields in one variable over number fields.
title First-order definability of Campana Points and Darmon Points in algebraic function fields in one variable over number fields
topic Number Theory
Algebraic Geometry
Logic
11U05 (Primary), 11E81, 12L05, 12F20 (secondary)
url https://arxiv.org/abs/2510.17042