CM points on Shimura curves via QM-equivariant isogeny volcanoes

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1. Verfasser: Saia, Frederick
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Veröffentlicht: 2022
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author Saia, Frederick
author_facet Saia, Frederick
contents We study CM points on the Shimura curves $X_0^D(N)_{/\mathbb{Q}}$ and $X_1^D(N)_{/\mathbb{Q}}$, parametrizing abelian surfaces with quaternionic multiplication and extra level structure. A description of the locus of points with CM by a specified order is obtained for general level, via an isogeny-volcano approach in analogy to work of Clark and Clark--Saia in the $D=1$ case of modular curves. This allows for a count of all points with CM by a specified order on such a curve, and a determination of all primitive residue fields and primitive degrees of such points on $X_0^D(N)_{/\mathbb{Q}}$. We leverage computations of least degrees towards the existence of sporadic CM points on $X_0^D(N)_{/\mathbb{Q}}$.
format Preprint
id arxiv_https___arxiv_org_abs_2212_12635
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle CM points on Shimura curves via QM-equivariant isogeny volcanoes
Saia, Frederick
Number Theory
We study CM points on the Shimura curves $X_0^D(N)_{/\mathbb{Q}}$ and $X_1^D(N)_{/\mathbb{Q}}$, parametrizing abelian surfaces with quaternionic multiplication and extra level structure. A description of the locus of points with CM by a specified order is obtained for general level, via an isogeny-volcano approach in analogy to work of Clark and Clark--Saia in the $D=1$ case of modular curves. This allows for a count of all points with CM by a specified order on such a curve, and a determination of all primitive residue fields and primitive degrees of such points on $X_0^D(N)_{/\mathbb{Q}}$. We leverage computations of least degrees towards the existence of sporadic CM points on $X_0^D(N)_{/\mathbb{Q}}$.
title CM points on Shimura curves via QM-equivariant isogeny volcanoes
topic Number Theory
url https://arxiv.org/abs/2212.12635