Title
Gluing Curves Of Genus 1 And 2 Along Their 2-Torsion
Abstract
Let X (resp. Y) be a curve of genus 1 (resp. 2) over a base field k whose characteristic does not equal 2. We give criteria for the existence of a curve Z over k whose Jacobian is up to twist (2, 2, 2)-isogenous to the products of the Jacobians of X and Y. Moreover, we give algorithms to construct the curve Z once equations for X and Y are given. The first of these is based on interpolation methods involving numerical results over C that are proved to be correct over general fields a posteriori, whereas the second involves the use of hyperplane sections of the Kummer variety of Y whose desingularization is isomorphic to X. As an application, we find a twist of a Jacobian over Q that admits a rational 70-torsion point.
Year
DOI
Venue
2021
10.1090/mcom/3627
MATHEMATICS OF COMPUTATION
Keywords
DocType
Volume
Gluing, Jacobians, isogenies, explicit aspects
Journal
90
Issue
ISSN
Citations 
331
0025-5718
0
PageRank 
References 
Authors
0.34
0
3
Name
Order
Citations
PageRank
Hanselman Jeroen100.34
Schiavone Sam200.34
Jeroen Sijsling322.27