Inverse limits of CM points on certain Shimura varieties

Fuente: arXiv
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Main Authors: Jung, Ho Yun, Koo, Ja Kyung, Shin, Dong Hwa
Format: Preprint
Published: 2025
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author Jung, Ho Yun
Koo, Ja Kyung
Shin, Dong Hwa
author_facet Jung, Ho Yun
Koo, Ja Kyung
Shin, Dong Hwa
contents Let $N$ be a positive integer, and let $D\equiv0$ or $1\Mod{4}$ be a negative integer. We define the sets $\mathcal{CM}(D,\,Y_1(N)^\pm)$ and $\mathcal{CM}(D,\,Y(N)^\pm)$ as subsets of the Shimura varieties $Y_1(N)^\pm$ and $Y(N)^\pm$, respectively, consisting of CM points of discriminant $D$ that are primitive modulo $N$. By using the theory of definite form class groups, we show that the inverse limits \begin{equation*} \varprojlim_N\,\mathcal{CM}(D,\,Y_1(N)^\pm)\quad\textrm{and}\quad \varprojlim_N\,\mathcal{CM}(D,\,Y(N)^\pm) \end{equation*} naturally inherit group structures isomorphic to $\mathrm{Gal}(K^\mathrm{ab}/\mathbb{Q})$ and $\mathrm{Gal}(K^\mathrm{ab}(t^{1/\infty})/\mathbb{Q}(t))$, respectively, where $K=\mathbb{Q}(\sqrt{D})$ and $t$ is a transcendental number. These results provide an explicit and geometric interpretation of class field theory in terms of inverse limits of CM points on the associated Shimura varieties.
format Preprint
id arxiv_https___arxiv_org_abs_2505_09163
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Inverse limits of CM points on certain Shimura varieties
Jung, Ho Yun
Koo, Ja Kyung
Shin, Dong Hwa
Number Theory
11R37, 11E57, 11G18
Let $N$ be a positive integer, and let $D\equiv0$ or $1\Mod{4}$ be a negative integer. We define the sets $\mathcal{CM}(D,\,Y_1(N)^\pm)$ and $\mathcal{CM}(D,\,Y(N)^\pm)$ as subsets of the Shimura varieties $Y_1(N)^\pm$ and $Y(N)^\pm$, respectively, consisting of CM points of discriminant $D$ that are primitive modulo $N$. By using the theory of definite form class groups, we show that the inverse limits \begin{equation*} \varprojlim_N\,\mathcal{CM}(D,\,Y_1(N)^\pm)\quad\textrm{and}\quad \varprojlim_N\,\mathcal{CM}(D,\,Y(N)^\pm) \end{equation*} naturally inherit group structures isomorphic to $\mathrm{Gal}(K^\mathrm{ab}/\mathbb{Q})$ and $\mathrm{Gal}(K^\mathrm{ab}(t^{1/\infty})/\mathbb{Q}(t))$, respectively, where $K=\mathbb{Q}(\sqrt{D})$ and $t$ is a transcendental number. These results provide an explicit and geometric interpretation of class field theory in terms of inverse limits of CM points on the associated Shimura varieties.
title Inverse limits of CM points on certain Shimura varieties
topic Number Theory
11R37, 11E57, 11G18
url https://arxiv.org/abs/2505.09163