Bhargava's local specification density conjecture for SnS_n-number fields

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Let nn be a positive integer, and let Σ=(Σ2,Σ3,Σ5,…)\Sigma=(\Sigma_2,\Sigma_3,\Sigma_5,\ldots) be an acceptable collection of local specifications, where each Σp\Sigma_p is a set of Qp\mathbb{Q}_p-algebras. For a local algebra FpF_p, write Disc⁡(Fp)\operatorname{Disc}(F_p) for its discriminant and Aut⁡Qp(Fp)\operatorname{Aut}_{\mathbb{Q}_p}(F_p) for its automorphism group. Bhargava's conjecture. As FF varies over SnS_n-number fields with fixed signature (r1,r2)(r_1,r_2) ordered by absolute discriminant,

Prob⁡(F∣F⊗QQp∈Σp)=∏p1c(n,p)(∑Fp∈Σp1Disc⁡(Fp)⋅1#Aut⁡Qp(Fp)).\operatorname{Prob}(F\mid F\otimes_{\mathbb{Q}}\mathbb{Q}_p\in\Sigma_p)=\prod_p\frac{1}{c(n,p)}\left(\sum_{F_p\in\Sigma_p}\frac{1}{\operatorname{Disc}(F_p)}\cdot\frac{1}{\#\operatorname{Aut}_{\mathbb{Q}_p}(F_p)}\right).

This predicts independence of local specifications with the mass prescribed by discriminants and automorphism groups; it is proved for SnS_n-fields of degree n≤5n\leq5, while the general case remains open.

References

Primary source

Benjamin Breen, “The 2-Selmer group of S_n-number fields of even degree”, arXiv:2110.00197 (2021).

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