Klingen Eisenstein series congruences and modularity

Fuente: arXiv
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Auteurs principaux: Berger, Tobias, Brown, Jim, Klosin, Krzysztof
Format: Preprint
Publié: 2025
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author Berger, Tobias
Brown, Jim
Klosin, Krzysztof
author_facet Berger, Tobias
Brown, Jim
Klosin, Krzysztof
contents We construct a mod $\ell$ congruence between a Klingen Eisenstein series (associated to a classical newform $ϕ$ of weight $k$) and a Siegel cusp form $f$ with irreducible Galois representation. We use this congruence to show non-vanishing of the Bloch-Kato Selmer group $H^1_f(\mathbf{Q}, \textrm{ad}^0ρ_ϕ(2-k)\otimes \mathbf{Q}_{\ell}/\mathbf{Z}_{\ell})$ under certain assumptions and provide an example. We then prove an $R=dvr$ theorem for the Fontaine-Laffaille universal deformation ring of $\overlineρ_f$ under some assumptions, in particular, that the residual Selmer group $H^1_f(\mathbf{Q}, \textrm{ad}^0\overlineρ_ϕ(k-2))$ is cyclic. For this we prove a result about extensions of Fontaine-Laffaille modules. We end by formulating conditions for when $H^1_f(\mathbf{Q}, \textrm{ad}^0\overlineρ_ϕ(k-2))$ is non-cyclic and the Eisenstein ideal is non-principal.
format Preprint
id arxiv_https___arxiv_org_abs_2501_10327
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Klingen Eisenstein series congruences and modularity
Berger, Tobias
Brown, Jim
Klosin, Krzysztof
Number Theory
11F33, 11F46, 11F80, 11F67
We construct a mod $\ell$ congruence between a Klingen Eisenstein series (associated to a classical newform $ϕ$ of weight $k$) and a Siegel cusp form $f$ with irreducible Galois representation. We use this congruence to show non-vanishing of the Bloch-Kato Selmer group $H^1_f(\mathbf{Q}, \textrm{ad}^0ρ_ϕ(2-k)\otimes \mathbf{Q}_{\ell}/\mathbf{Z}_{\ell})$ under certain assumptions and provide an example. We then prove an $R=dvr$ theorem for the Fontaine-Laffaille universal deformation ring of $\overlineρ_f$ under some assumptions, in particular, that the residual Selmer group $H^1_f(\mathbf{Q}, \textrm{ad}^0\overlineρ_ϕ(k-2))$ is cyclic. For this we prove a result about extensions of Fontaine-Laffaille modules. We end by formulating conditions for when $H^1_f(\mathbf{Q}, \textrm{ad}^0\overlineρ_ϕ(k-2))$ is non-cyclic and the Eisenstein ideal is non-principal.
title Klingen Eisenstein series congruences and modularity
topic Number Theory
11F33, 11F46, 11F80, 11F67
url https://arxiv.org/abs/2501.10327