The spectrum of the symplectic Grassmannian and $\mathrm{Mat}_{n,m}$

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1. Verfasser: Droschl, Johannes
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Veröffentlicht: 2025
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author Droschl, Johannes
author_facet Droschl, Johannes
contents Let $\mathbf{G}$ be a reductive group and $\mathbf{X}$ a spherical $\mathbf{G}$-variety over a local non-archimedean field $\mathbb{F}$. We denote by $S(\mathbf{X}(\mathbb{F}))$ the Schwartz-functions on $\mathbf{X}(\mathbb{F})$. In this paper we offer a new approach on how to obtain bounds on \[\dim_{\mathbb{C}}\mathrm{Hom}_{\mathbf{G}(\mathbb{F})}(S(\mathbf{X}(\mathbb{F})),π)\]for an irreducible smooth representation $π$ of $\mathbf{G}(\mathbb{F})$. Our strategy builds on the theory of $ρ$-derivatives and the Local Structure Theorem for spherical varieties. Currently, we focus on the case of the symplectic Grassmannian and the space of matrices. In particular, we obtain a new proof of Howe duality in type II as well as an explicit description of the local Miyawaki-liftings in the Hilbert-Siegel case. Furthermore, we manage to extend previous results of the author regarding the conservation relation in the theta correspondence to metaplectic covers of symplectic groups. Finally, we use our new proof of Howe duality in type II to relate the order of the poles of Godement-Jacquet $L$-functions to the geometry of the space of matrices and the order of poles of certain intertwining operators.
format Preprint
id arxiv_https___arxiv_org_abs_2506_13530
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The spectrum of the symplectic Grassmannian and $\mathrm{Mat}_{n,m}$
Droschl, Johannes
Representation Theory
11F70, 22E46, 22E50
Let $\mathbf{G}$ be a reductive group and $\mathbf{X}$ a spherical $\mathbf{G}$-variety over a local non-archimedean field $\mathbb{F}$. We denote by $S(\mathbf{X}(\mathbb{F}))$ the Schwartz-functions on $\mathbf{X}(\mathbb{F})$. In this paper we offer a new approach on how to obtain bounds on \[\dim_{\mathbb{C}}\mathrm{Hom}_{\mathbf{G}(\mathbb{F})}(S(\mathbf{X}(\mathbb{F})),π)\]for an irreducible smooth representation $π$ of $\mathbf{G}(\mathbb{F})$. Our strategy builds on the theory of $ρ$-derivatives and the Local Structure Theorem for spherical varieties. Currently, we focus on the case of the symplectic Grassmannian and the space of matrices. In particular, we obtain a new proof of Howe duality in type II as well as an explicit description of the local Miyawaki-liftings in the Hilbert-Siegel case. Furthermore, we manage to extend previous results of the author regarding the conservation relation in the theta correspondence to metaplectic covers of symplectic groups. Finally, we use our new proof of Howe duality in type II to relate the order of the poles of Godement-Jacquet $L$-functions to the geometry of the space of matrices and the order of poles of certain intertwining operators.
title The spectrum of the symplectic Grassmannian and $\mathrm{Mat}_{n,m}$
topic Representation Theory
11F70, 22E46, 22E50
url https://arxiv.org/abs/2506.13530