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Proposition 4.1

Proved
LocalConjugacy.proposition_4_1

by burkh4rt · Sep 30, 2026 · Mathlib 0df444a (Lean v4.33.1)

group-theorylocal-conjugacynonabelian-cohomologyprofinite-groups

In a profinite group GGG, suppose H,H′≤GH,H'\leq GH,H′≤G each supplement some abelian N⊴GN\trianglelefteq GN⊴G. If for each prime ppp, HHH contains a conjugate of some Sylow ppp-subgroup of H′H'H′, then HHH contains a conjugate of H′H'H′.

Preamble
import Definitions.Def_LocalConjugacy_Groups

/-
Proposition 4.1: the abelian subgroup N and both supplements are closed.
No solvability assumption is made on G.

This is an open draft target. The deliberate `sorry` is the target proof hole;
all definitions and the structural proofs on which the statement rests compile
without admitted proofs.
-/
universe u v
open LocalConjugacy
Formal statement
theorem LocalConjugacy.proposition_4_1 {G : ProfiniteGrp.{u}} (N H K : Subgroup G) [N.Normal]
    (hN : IsClosed (N : Set G)) (hH : IsClosed (H : Set G))
    (hK : IsClosed (K : Set G)) [IsMulCommutative N]
    (hHN : Supplements N H) (hKN : Supplements N K)
    (hlocal : LocallyContains H K) : ∃ g : G, conjugate g K ≤ H := by sorry
Source
Michael C. Burkhart, Local conjugacy in prosolvable groups, arXiv:2609.37678v1 (29 September 2026), https://arxiv.org/pdf/2609.37678v1, p. 7, Proposition 4.1; standing conventions in §1.2, pp. 2–3.
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What the Lean code literally says, in plain math · GPT-6 family (exact model variant not exposed)

For every profinite group GGG in universe uuu and closed subgroups N,H,K≤GN,H,K\le GN,H,K≤G, suppose that NNN is normal in GGG and its multiplication is commutative, and that every element of GGG can be expressed both as nhnhnh with n∈N,h∈Hn\in N,h\in Hn∈N,h∈H and as n′kn'kn′k with n′∈N,k∈Kn'\in N,k\in Kn′∈N,k∈K. Suppose also that for every natural prime ppp there exist a Sylow pro-ppp subgroup PpP_pPp​ of KKK and an element gp∈Gg_p\in Ggp​∈G with gpPpgp−1≤Hg_pP_pg_p^{-1}\le Hgp​Pp​gp−1​≤H. Then there exists a single g∈Gg\in Gg∈G with gKg−1≤HgKg^{-1}\le HgKg−1≤H. A Sylow pro-ppp subgroup PPP of a subgroup A≤GA\le GA≤G means a subgroup P≤AP\le AP≤A that is closed in GGG, for which every quotient P/UP/UP/U by an open normal subgroup of PPP has the property that every element is killed by some power pkp^kpk with k∈Nk\in\mathbb Nk∈N, and that is maximal under inclusion among the closed subgroups of GGG contained in AAA with this quotient property. The product expressions need not be unique, and neither intersection with NNN is required to be trivial. The conclusion is containment rather than equality. Neither the local subgroup nor its conjugating element must be independent of ppp. All natural primes are included; trivial groups, trivial NNN, and trivial Sylow subgroups are permitted, and none of these groups is required to be finite.

Human review
  • Endorsed by Shuze Chen · Sep 30, 2026

    Confirmed by the moderator at approval.

  • Endorsed by burkh4rt · Sep 30, 2026

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

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