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阿代尔标架型类群与显式类域论

Adelic framed form class groups and explicit class field theory

Ja Kyung Koo, Dong Hwa Shin, Dong Sung Yoon

arXiv 2608.04873首次发表:更新:

AI 中文总结

本文研究负判别式虚二次域,定义阿代尔标架型类群,证明其与特定伽罗瓦群同构,整合经典数论概念,且该类群的抽象结构唯一确定对应虚二次域。

AI 中文摘要

设D为负判别式,令K=ℚ(√D),记𝒬(D)为ℤ上判别式为D的本原正定二元二次型集合。我们引入阿代尔标架型集合\\(\widehat{\mathcal{Q}}(D)=\left\{(Q,\\,\gamma)\in \mathcal{Q}(D)\times\mathrm{SL}_2(\widehat{\mathbb{Z}})~|~ Q\left(\gamma\begin{bmatrix}1\\\\0\end{bmatrix}\right)\in \widehat{\mathbb{Z}}^\times\right\}\\)及其在\\(\mathrm{SL}_2(\mathbb{Z})\\)自然作用下的轨道空间\\(\widehat{C}(D)\\)。我们在\\(\widehat{C}(D)\\)上定义高斯-狄利克雷合成律的显式阿代尔类比,并赋予其由\\(\widehat{\mathcal{Q}}(D)\\)的子空间拓扑诱导的商拓扑,其中\\(\mathcal{Q}(D)\\)取离散拓扑,\\(\mathrm{SL}_2(\widehat{\mathbb{Z}})\\)取 profinite 拓扑。随后我们证明存在拓扑群同构\\(\widehat{C}(D)\simeq\mathrm{Gal}\left(K^\mathrm{ab}(\mathfrak{t}^{1/\infty})/K(\mathfrak{t})\right)\\),其中伽罗瓦群赋予克鲁尔拓扑,\\(\mathfrak{t}\\)为正超越实数,\\(\mathfrak{t}^{1/\infty}=\{\sqrt[N]{\mathfrak{t}}~|~N\geq1\}\\)。此外,我们将\\(\widehat{C}(D)\\)的一个显式定义子群与\\(\mathrm{Gal}(K^\mathrm{ab}/K)\\)等同,并描述其对模函数特殊值的对应伽罗瓦作用,由此在单一阿代尔框架下整合经典高斯合成、有限层型类群与志村互反律。最后我们证明\\(\widehat{C}(D)\\)的抽象群结构唯一确定虚二次域K。

英文摘要

Let $D$ be a negative discriminant, and let $K=\mathbb{Q}(\sqrt{D})$. Let $\mathcal{Q}(D)$ denote the set of primitive positive definite binary quadratic forms over $\mathbb{Z}$ of discriminant $D$. We introduce the set of adelic framed forms \begin{equation*} \widehat{\mathcal{Q}}(D)= \left\{(Q,\,γ)\in \mathcal{Q}(D)\times\mathrm{SL}_2(\widehat{\mathbb{Z}})~|~ Q\left(γ\begin{bmatrix}1\\0\end{bmatrix}\right)\in \widehat{\mathbb{Z}}^\times\right\} \end{equation*} and its orbit space $\widehat{C}(D)$ under the natural action of $\mathrm{SL}_2(\mathbb{Z})$. We define an explicit adelic analogue of the Gauss-Dirichlet composition law on $\widehat{C}(D)$ and endow $\widehat{C}(D)$ with the quotient topology induced by the subspace topology on $\widehat{\mathcal{Q}}(D)$ inherited from the product topology on $\mathcal{Q}(D)\times\mathrm{SL}_2(\widehat{\mathbb{Z}})$, where $\mathcal{Q}(D)$ is discrete and $\mathrm{SL}_2(\widehat{\mathbb{Z}})$ has its profinite topology. We then prove that there is an isomorphism of topological groups \begin{equation*} \widehat{C}(D)\simeq\mathrm{Gal}\left(K^\mathrm{ab}(\mathfrak{t}^{1/\infty})/K(\mathfrak{t})\right), \end{equation*} where the Galois group is endowed with the Krull topology, $\mathfrak{t}$ is a positive transcendental real number, and $\mathfrak{t}^{1/\infty}=\{\sqrt[N]{\mathfrak{t}}~|~N\geq1\}$. Moreover, we identify an explicitly defined subgroup of $\widehat{C}(D)$ with $\mathrm{Gal}(K^\mathrm{ab}/K)$ and describe the corresponding Galois action on special values of modular functions. In this way, classical Gauss composition, finite-level form class groups, and Shimura reciprocity are brought together within a single adelic framework. Finally, we show that the abstract group structure of $\widehat{C}(D)$ uniquely determines the imaginary quadratic field $K$.

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