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arXiv · 2407.14450

Generalized class group actions on oriented elliptic curves with level structure

Sarah Arpin·Wouter Castryck·Jonathan Komada Eriksen·Gioella Lorenzon·Frederik Vercauteren
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Abstract

We study a large family of generalized class groups of imaginary quadratic orders $O$ and prove that they act freely and (essentially) transitively on the set of primitively $O$-oriented elliptic curves over a field $k$ (assuming this set is non-empty) equipped with appropriate level structure. This extends, in several ways, a recent observation due to Galbraith, Perrin and Voloch for the ray class group. We show that this leads to a reinterpretation of the action of the class group of a suborder $O' \subseteq O$ on the set of $O'$-oriented elliptic curves, discuss several other examples, and briefly comment on the hardness of the corresponding vectorization problems.

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Sarah Arpin, Wouter Castryck, Jonathan Komada Eriksen, Gioella Lorenzon, Frederik Vercauteren. 2024-07-19. Generalized class group actions on oriented elliptic curves with level structure. https://doi.org/10.1007/978-3-031-81824-0_12

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