Integer-valued polynomials and $p$-adic Fourier theory

Fuente: arXiv
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Main Authors: Berger, Laurent, Sprang, Johannes
Format: Preprint
Published: 2025
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author Berger, Laurent
Sprang, Johannes
author_facet Berger, Laurent
Sprang, Johannes
contents The goal of this paper is to give a numerical criterion for an open question in $p$-adic Fourier theory. Let $F$ be a finite extension of $\mathbf{Q}_p$. Schneider and Teitelbaum defined and studied the character variety $\mathfrak{X}$, which is a rigid analytic curve over $F$ that parameterizes the set of locally $F$-analytic characters $λ: (o_F,+) \to (\mathbf{C}_p^\times,\times)$. Determining the structure of the ring $Λ_F(\mathfrak{X})$ of bounded-by-one functions on $\mathfrak{X}$ defined over $F$ seems like a difficult question. Using the Katz isomorphism, we prove that if $F= \mathbf{Q}_{p^2}$, then $Λ_F(\mathfrak{X}) = o_F [\![o_F]\!]$ if and only if the $o_F$-module of integer-valued polynomials on $o_F$ is generated by a certain explicit set. Some computations in SageMath indicate that this seems to be the case.
format Preprint
id arxiv_https___arxiv_org_abs_2502_18053
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Integer-valued polynomials and $p$-adic Fourier theory
Berger, Laurent
Sprang, Johannes
Number Theory
The goal of this paper is to give a numerical criterion for an open question in $p$-adic Fourier theory. Let $F$ be a finite extension of $\mathbf{Q}_p$. Schneider and Teitelbaum defined and studied the character variety $\mathfrak{X}$, which is a rigid analytic curve over $F$ that parameterizes the set of locally $F$-analytic characters $λ: (o_F,+) \to (\mathbf{C}_p^\times,\times)$. Determining the structure of the ring $Λ_F(\mathfrak{X})$ of bounded-by-one functions on $\mathfrak{X}$ defined over $F$ seems like a difficult question. Using the Katz isomorphism, we prove that if $F= \mathbf{Q}_{p^2}$, then $Λ_F(\mathfrak{X}) = o_F [\![o_F]\!]$ if and only if the $o_F$-module of integer-valued polynomials on $o_F$ is generated by a certain explicit set. Some computations in SageMath indicate that this seems to be the case.
title Integer-valued polynomials and $p$-adic Fourier theory
topic Number Theory
url https://arxiv.org/abs/2502.18053