The discriminant norm conjecture for cubic roots

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Let u∈Sdu\in S_d, write ν=u1/3\nu=u^{1/3}, and let c=c(u)c=c(u) be the product of the distinct rational primes dividing uu but not dd. Let c′c' be the odd part of cc. Let F=Q(−3d)F=\mathbb{Q}(\sqrt{-3d}), let McM_c be the corresponding ring class field, and let D(F(ν)/F)D(F(\nu)/F) denote the relative discriminant. Discriminant norm conjecture. If ν∈Mc\nu\in M_c, then

N(D(F(ν)/F)c−4)={1,3∤d,36,3∣d,N\left(D(F(\nu)/F)c^{-4}\right)= \begin{cases} 1,&3\nmid d,\\ 3^6,&3\mid d, \end{cases}

and if ν∉Mc\nu\notin M_c, then

N(D(F(ν)/F)c−4)={38,3∤d,318,3∣d.N\left(D(F(\nu)/F)c^{-4}\right)= \begin{cases} 3^8,&3\nmid d,\\ 3^{18},&3\mid d. \end{cases}

When d≡3(mod4)d\equiv3\pmod 4, each occurrence of c−4c^{-4} is instead replaced by c′−4c'^{-4}. The conjecture predicts precise discriminant norms according to whether the cubic root lies in the relevant ring class field, complementing the paper's class-field criteria and numerical evidence.

References

Primary source

R. Evans, F. Lemmermeyer, Z. -H. Sun and M. van Veen, “Ring class fields and a result of Hasse”, arXiv:2403.04986 (2024).

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