Explicit constructions of cyclic N-isogenies

Fuente: arXiv
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Main Authors: Jeon, Daeyeol, Kwon, Yongjae
Format: Preprint
Published: 2025
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author Jeon, Daeyeol
Kwon, Yongjae
author_facet Jeon, Daeyeol
Kwon, Yongjae
contents The modular curve X_0(N) parametrizes elliptic curves together with a cyclic subgroup of order N, and hence cyclic N-isogenies. While explicit moduli descriptions of X_1(N) are well developed, a comparable construction for X_0(N) has remained incomplete. We give a uniform method for constructing explicit generators of C(X_0(N)), extending an approach of Dowd, and use them to obtain a concrete moduli interpretation of cyclic N-isogenies. This yields explicit formulas for sporadic rational points on X_0(N) and the associated isogenies, providing a unified solution to the moduli problem for X_0(N).
format Preprint
id arxiv_https___arxiv_org_abs_2512_21088
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Explicit constructions of cyclic N-isogenies
Jeon, Daeyeol
Kwon, Yongjae
Number Theory
11G05, 11G18
The modular curve X_0(N) parametrizes elliptic curves together with a cyclic subgroup of order N, and hence cyclic N-isogenies. While explicit moduli descriptions of X_1(N) are well developed, a comparable construction for X_0(N) has remained incomplete. We give a uniform method for constructing explicit generators of C(X_0(N)), extending an approach of Dowd, and use them to obtain a concrete moduli interpretation of cyclic N-isogenies. This yields explicit formulas for sporadic rational points on X_0(N) and the associated isogenies, providing a unified solution to the moduli problem for X_0(N).
title Explicit constructions of cyclic N-isogenies
topic Number Theory
11G05, 11G18
url https://arxiv.org/abs/2512.21088