Zywina's agreeable-closure classification for rational non-CM -invariants
Zywina's agreeable-closure classification for rational non-CM -invariants
Let be a non-CM rational -invariant. Write for the associated adelic Galois-image subgroup, let be its agreeable closure, and let be the corresponding modular curve. Zywina's agreeable-closure classification. If the modular curve has infinitely many rational points, then the intersection is one of the conjugacy classes given in the paper's table of infinite special-linear intersections. On the other hand, if has finitely many rational points, then and are given in the paper's table of exceptional -invariants. This is a conjectural classification of the possible agreeable closures, and hence of the intersections with , for non-CM elliptic curves over ; the stated alternatives organize the cases according to whether the associated modular curve has infinitely or finitely many rational points.
Sources & referencesView supporting material
Primary source
Kenji Terao, “Degrees of points with rational j-invariant on X_0(n) and X_1(n)”, arXiv:2507.13199 (2025).
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