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Main Authors: Nguyen, Chi, Yagci, Arman, Zhou, Yunchuan
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2601.17559
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author Nguyen, Chi
Yagci, Arman
Zhou, Yunchuan
author_facet Nguyen, Chi
Yagci, Arman
Zhou, Yunchuan
contents Primitive points on the tower of modular curves $X_1(n)$ provide a finite "certificate set" for detecting isolated points above a fixed $j$-invariant: for a non-CM elliptic curve $E/\mathbb{Q}$, $j(E)$ arises from an isolated point on some $X_1(N)$ if and only if one of the associated primitive point is isolated. We bound the number $\lvert \mathcal{P}(E)\rvert$ of primitive points in terms of the adelic index $I(E)$ and give criteria as well as an algorithm for uniqueness of primitive point. As an application, every Serre curve has $\lvert \mathcal{P}(E)\rvert =1$; hence Serre curves do not contribute isolated $j$-invariants.
format Preprint
id arxiv_https___arxiv_org_abs_2601_17559
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Local Transitivity and Entanglement Obstructions for Primitive Points
Nguyen, Chi
Yagci, Arman
Zhou, Yunchuan
Number Theory
14H52, 11F80
Primitive points on the tower of modular curves $X_1(n)$ provide a finite "certificate set" for detecting isolated points above a fixed $j$-invariant: for a non-CM elliptic curve $E/\mathbb{Q}$, $j(E)$ arises from an isolated point on some $X_1(N)$ if and only if one of the associated primitive point is isolated. We bound the number $\lvert \mathcal{P}(E)\rvert$ of primitive points in terms of the adelic index $I(E)$ and give criteria as well as an algorithm for uniqueness of primitive point. As an application, every Serre curve has $\lvert \mathcal{P}(E)\rvert =1$; hence Serre curves do not contribute isolated $j$-invariants.
title Local Transitivity and Entanglement Obstructions for Primitive Points
topic Number Theory
14H52, 11F80
url https://arxiv.org/abs/2601.17559