Class number formula conjecture for split primes 7 and 11

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Let Kd=Q(−d)K_d = \mathbb{Q}(\sqrt{-d}) be an imaginary quadratic field in which (p)=pp′(p)=\mathfrak{p}\mathfrak{p}' splits, where p=7p=7 or 1111. Let f=p′\mathfrak{f}=\mathfrak{p}' be a first-degree prime ideal, write −d=dKf2-d=d_Kf^2, and assume Np=pN\mathfrak{p}=p. Put O=R−d\mathcal{O}=\textsf{R}_{-d} and define

τp=(Fd/Kdp),\tau_{\mathfrak{p}}=\left(\frac{F_d/K_d}{\mathfrak{p}}\right),

where FdF_d is the inertia field for p\mathfrak{p} in the extended ring class field LO,p=ΣpΩpfL_{\mathcal{O},p}=\Sigma_p\Omega_{pf}. Define

Dn,p={−d ∣(−dp)=+1 ∧ord⁡(τp)=n}.\mathfrak{D}_{n,p}=\Big\{-d\ \bigg|\left(\frac{-d}{p}\right)=+1\ \wedge \operatorname{ord}(\tau_{\mathfrak{p}})=n\Big\}.

Class number formula conjecture. For n>1n>1,

∑−d∈Dn,ph(−d)=2φ(f)∑k∣nμ(n/k)pk.\sum_{-d\in\mathfrak{D}_{n,p}}h(-d)=\frac{2}{\varphi(\mathfrak{f})}\sum_{k\mid n}\mu(n/k)p^k.

This conjecture extends the class-number formulas obtained by the same method for p=2,3,5p=2,3,5 to the cases p=7p=7 and p=11p=11. Its status is not resolved in the supplied source context.

References

Primary source

Sushmanth J. Akkarapakam and Patrick Morton, “Algebraic functions and class number formulas”, arXiv:2511.00583 (2025).

Additional references

4 papers in this index state this conjecture (2011–2025). The statement above is taken from the most recent of them; the others are arXiv:2506.13749, arXiv:1410.2921, arXiv:1102.4844.

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