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Proper-subgroup Hilbert degrees in the Weierstrass extension

Proved
WeierstrassEllipticZeta.philippon_subgroup_degree_profile

by tomasz · Sep 23, 2026 · Mathlib 0df444a (Lean v4.33.1)

algebraic-geometrynumber-theory

Use the period pair, sigma differential data, and entire functions

S=σ3(1,℘,℘′,ζ,℘′ζ+2℘2)S=\sigma^3(1,\wp,\wp',\zeta,\wp'\zeta+2\wp^2)S=σ3(1,℘,℘′,ζ,℘′ζ+2℘2)

off the period lattice Λ\LambdaΛ, with no common zero. Let MMM be any compatible Philippon model of these functions. For every proper connected Zariski closed algebraic subgroup HHH of its group, put K=φ−1(H)K=\varphi^{-1}(H)K=φ−1(H), an integer submodule of C\mathbb CC.

At least one of the following alternatives holds:

  1. K={0}K=\{0\}K={0} and H(H;m,n)≥1\mathcal H(H;m,n)\ge1H(H;m,n)≥1 for every positive integer pair m,nm,nm,n.
  2. K⊆ΛK\subseteq\LambdaK⊆Λ and H(H;m,n)≥m\mathcal H(H;m,n)\ge mH(H;m,n)≥m for every positive integer pair m,nm,nm,n.

The branch is chosen before m,nm,nm,n. Both branches may hold. The degree form is the factorial-normalized top part of the actual quotient Hilbert polynomial of the embedded subgroup’s vanishing ideal, not an assigned numerical degree. Under its general definition the polynomial is zero if an eventual Hilbert polynomial does not exist, so its required existence and positivity must be established in proving this statement.

This is a proved geometric application theorem in Senthil. It combines the extension’s proper-subgroup projection classification with the nonempty-variety degree bound and the stronger mixed-degree bound when projection onto the additive factor is surjective. It has no finite sample, contact order, polynomial vanishing hypothesis, or multiplicity conclusion.

Preamble
import Definitions.Def_WeierstrassEllipticZeta_PhilipponModel

set_option autoImplicit false
open WeierstrassEllipticZeta WeierstrassEllipticZeta.PhilipponApplication
open PhilipponMultiplicity
Formal statement
theorem WeierstrassEllipticZeta.philippon_subgroup_degree_profile    (L : PeriodPair) (D : EllipticSigmaDifferentialData L)
    (S : Fin 5 → ℂ → ℂ)
    (hS : ∀ j, AnalyticOnNhd ℂ (S j) Set.univ)
    (hS_value : ∀ z : ℂ, z ∉ L.lattice → ∀ j : Fin 5,
      S j z = D.sigma z ^ 3 * ![1, L.weierstrassP z, L.derivWeierstrassP z,
        weierstrassZeta L z,
        L.derivWeierstrassP z * weierstrassZeta L z + 2 * L.weierstrassP z ^ 2] j)
    (hS_ne : ∀ z : ℂ, ∃ j : Fin 5, S j z ≠ 0)
    (M : Model S) (H : AlgebraicSubgroup M.group)
    (hH : H.IsConnected) (hproper : H.carrier ≠ Set.univ) :
    ((M.pullbackSubmodule H = ⊥) ∧
      ∀ m n : ℕ, 1 ≤ m → 1 ≤ n →
        1 ≤ hilbertDegreeForm M.group H.carrier ![m, n]) ∨
    ((M.pullbackSubmodule H ≤ L.lattice) ∧
      ∀ m n : ℕ, 1 ≤ m → 1 ≤ n →
        (m : ℝ) ≤ hilbertDegreeForm M.group H.carrier ![m, n]) := by sorry
Source
Senthil Kumar, Appendix A, application geometry, https://doi.org/10.1017/S001309152610145X; Philippon (1986), Theorem 2.1 and Lemma 3.4, https://numdam.org/articles/10.24033/bsmf.2060/. Explicit application lemma in Senthil; not a numbered theorem in Philippon.
Human review
  • Endorsed by Shuze Chen · Sep 29, 2026

    Confirmed by the moderator at approval.

  • Endorsed by tomasz · Sep 29, 2026

    Confirmed by the mission captain (proposal self-audit).

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