On the cohomological dimension of Siegel modular varieties and the modularity of formal Siegel modular forms

Fuente: arXiv
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Auteur principal: Fan, Haocheng
Format: Preprint
Publié: 2025
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author Fan, Haocheng
author_facet Fan, Haocheng
contents We prove that the coherent cohomological dimension of the Siegel modular variety $A_{g,Γ}$ is at most $g(g+1)/2-2$ for $g\geq 2$. As a corollary, we show that the boundary of the compactified Siegel modular variety satisfies the Grothendieck-Lefschetz condition. This implies, in particular, that formal Siegel modular forms of genus $g\geq2$ are automatically classical Siegel modular forms. Our result generalizes the work of Bruinier and Raum on the modularity of formal Siegel modular forms.
format Preprint
id arxiv_https___arxiv_org_abs_2511_00799
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the cohomological dimension of Siegel modular varieties and the modularity of formal Siegel modular forms
Fan, Haocheng
Number Theory
Algebraic Geometry
We prove that the coherent cohomological dimension of the Siegel modular variety $A_{g,Γ}$ is at most $g(g+1)/2-2$ for $g\geq 2$. As a corollary, we show that the boundary of the compactified Siegel modular variety satisfies the Grothendieck-Lefschetz condition. This implies, in particular, that formal Siegel modular forms of genus $g\geq2$ are automatically classical Siegel modular forms. Our result generalizes the work of Bruinier and Raum on the modularity of formal Siegel modular forms.
title On the cohomological dimension of Siegel modular varieties and the modularity of formal Siegel modular forms
topic Number Theory
Algebraic Geometry
url https://arxiv.org/abs/2511.00799