Rationality and arithmetic of the moduli of abelian varieties

Fuente: arXiv
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Autores principales: Loughran, Daniel, Sankaran, Gregory
Formato: Preprint
Publicado: 2023
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author Loughran, Daniel
Sankaran, Gregory
author_facet Loughran, Daniel
Sankaran, Gregory
contents We study the rationality properties of the moduli space $\mathcal{A}_g$ of principally polarised abelian $g$-folds over $\mathbb{Q}$ and apply the results to arithmetic questions. In particular we show that any principally polarised abelian threefold over $\mathbb{F}_p$ may be lifted to an abelian variety over $\mathbb{Q}$. This is a phenomenon of low dimension: assuming the Bombieri-Lang conjecture we also show that this is not the case for abelian varieties of dimension at least seven. About moduli spaces, we show that $\mathcal{A}_g$ is unirational over $\mathbb{Q}$ for $g \leq 5$ and stably rational for $g=3$. This also allows us to make unconditional one of the results of Masser and Zannier about the existence of abelian varieties over $\mathbb{Q}$ that are not isogenous to Jacobians.
format Preprint
id arxiv_https___arxiv_org_abs_2310_01244
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Rationality and arithmetic of the moduli of abelian varieties
Loughran, Daniel
Sankaran, Gregory
Algebraic Geometry
Number Theory
(14K10), 14K15, 14H40, 14D23, 14M20, 14G12, 11G10
We study the rationality properties of the moduli space $\mathcal{A}_g$ of principally polarised abelian $g$-folds over $\mathbb{Q}$ and apply the results to arithmetic questions. In particular we show that any principally polarised abelian threefold over $\mathbb{F}_p$ may be lifted to an abelian variety over $\mathbb{Q}$. This is a phenomenon of low dimension: assuming the Bombieri-Lang conjecture we also show that this is not the case for abelian varieties of dimension at least seven. About moduli spaces, we show that $\mathcal{A}_g$ is unirational over $\mathbb{Q}$ for $g \leq 5$ and stably rational for $g=3$. This also allows us to make unconditional one of the results of Masser and Zannier about the existence of abelian varieties over $\mathbb{Q}$ that are not isogenous to Jacobians.
title Rationality and arithmetic of the moduli of abelian varieties
topic Algebraic Geometry
Number Theory
(14K10), 14K15, 14H40, 14D23, 14M20, 14G12, 11G10
url https://arxiv.org/abs/2310.01244