Curve equations from expansions of 1-forms at a nonrational point

Fuente: arXiv
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Autores principales: van Bommel, Raymond, Costa, Edgar, Poonen, Bjorn, Srinivasan, Padmavathi
Formato: Preprint
Publicado: 2025
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author van Bommel, Raymond
Costa, Edgar
Poonen, Bjorn
Srinivasan, Padmavathi
author_facet van Bommel, Raymond
Costa, Edgar
Poonen, Bjorn
Srinivasan, Padmavathi
contents We exhibit an algorithm to compute equations of an algebraic curve over a computable characteristic 0 field from the power series expansions of its regular 1-forms at a nonrational point of the curve, extending a 2005 algorithm of Baker, González-Jiménez, González, and Poonen for expansions at a rational point. If the curve is hyperelliptic, the equations present it as an explicit double cover of a smooth plane conic, or as a double cover of the projective line when possible. If the curve is nonhyperelliptic, the equations cut out the canonical model. The algorithm has been used to compute equations over $\mathbb{Q}$ for many hyperelliptic modular curves without a rational cusp in the L-functions and Modular Forms Database.
format Preprint
id arxiv_https___arxiv_org_abs_2506_14026
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Curve equations from expansions of 1-forms at a nonrational point
van Bommel, Raymond
Costa, Edgar
Poonen, Bjorn
Srinivasan, Padmavathi
Number Theory
14Q05 (Primary) 11G18, 14G35 (Secondary)
We exhibit an algorithm to compute equations of an algebraic curve over a computable characteristic 0 field from the power series expansions of its regular 1-forms at a nonrational point of the curve, extending a 2005 algorithm of Baker, González-Jiménez, González, and Poonen for expansions at a rational point. If the curve is hyperelliptic, the equations present it as an explicit double cover of a smooth plane conic, or as a double cover of the projective line when possible. If the curve is nonhyperelliptic, the equations cut out the canonical model. The algorithm has been used to compute equations over $\mathbb{Q}$ for many hyperelliptic modular curves without a rational cusp in the L-functions and Modular Forms Database.
title Curve equations from expansions of 1-forms at a nonrational point
topic Number Theory
14Q05 (Primary) 11G18, 14G35 (Secondary)
url https://arxiv.org/abs/2506.14026