Isogeny invariance conjecture for valuations of elliptic-curve j-invariants

Let OK\mathcal{O}_K be a discrete valuation domain with field of fractions KK and residue field kk, and let vv be the normalized valuation on KK. Let E1/KE_1/K and E2/KE_2/K be elliptic curves admitting an isogeny of degree dd from E1E_1 to E2E_2, where dd is coprime to char(k)\operatorname{char}(k). Isogeny valuation conjecture. If char(k)=2\operatorname{char}(k)=2 and 0<v(j(E1))<15v(2)0<v(j(E_1))<15v(2), then v(j(E1))=v(j(E2))v(j(E_1))=v(j(E_2)); if char(k)=3\operatorname{char}(k)=3 and 0<v(j(E1))<3v(3)0<v(j(E_1))<3v(3), then the same equality holds, and moreover, if ell1(mod3)ell\equiv1\pmod3 and 0<v(j(E1))<92v(3)0<v(j(E_1))<\frac92v(3), it still holds; and if char(k)=5\operatorname{char}(k)=5 and 0<v(j(E1))<3v(5)0<v(j(E_1))<3v(5), then v(j(E1))=v(j(E2))v(j(E_1))=v(j(E_2)). This conjecture is stated as implied by the main congruence conjecture and connects modular-polynomial divisibility with the behavior of isogenous elliptic curves over discretely valued fields.

Sources & referencesView supporting material

Primary source

Haiyang Wang, “Congruence properties of the coefficients of the classical modular polynomials”, arXiv:2406.01986 (2024).

Additional references

2 papers in this index state this conjecture (2017–2024). The statement above is taken from the most recent of them; the others are arXiv:1704.04893.

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