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Corollary 1.3

Proved
LocalConjugacy.corollary_1_3

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

group-theorylocal-conjugacynonabelian-cohomologyprofinite-groups

Let HHH be a closed subgroup of a profinite semidirect product G=N⋊JG=N\rtimes JG=N⋊J where NNN is pronilpotent and either GGG is prosupersolvable or JJJ is pronilpotent. If N∩H⊴NN\cap H\trianglelefteq NN∩H⊴N and HHH contains a conjugate of some Sylow ppp-subgroup of JJJ for each prime ppp, then HHH contains a conjugate of JJJ.

Preamble
import Definitions.Def_LocalConjugacy_Groups

/-
Corollary 1.3: an internal complement models the profinite semidirect product.
Normality of N ∩ H is required inside N, and local witnesses may vary with p.

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.corollary_1_3 {G : ProfiniteGrp.{u}} (N J H : Subgroup G)
    (hN : IsClosed (N : Set G)) (hJ : IsClosed (J : Set G))
    (hH : IsClosed (H : Set G)) (hsplit : Splits N J)
    (hpron : Pronilpotent N) (hcase : Prosupersolvable G ∨ Pronilpotent J)
    (hnormal : IntersectionNormal N H) (hlocal : LocallyContains H J) :
    ∃ g : G, conjugate g J ≤ 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. 2, Corollary 1.3; 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,J,H≤GN,J,H\le GN,J,H≤G, assume that NNN is normal in GGG, that every element of GGG has a unique expression njnjnj with n∈Nn\in Nn∈N and j∈Jj\in Jj∈J, that NNN is pronilpotent, and that either GGG is prosupersolvable or JJJ is pronilpotent. Assume also that N∩HN\cap HN∩H, regarded as a subgroup of NNN, is normal in NNN, and that for every natural prime ppp there exist a Sylow pro-ppp subgroup PpP_pPp​ of JJJ 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 one g∈Gg\in Gg∈G such that gJg−1≤HgJg^{-1}\le HgJg−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. Saying that a topological group RRR is pronilpotent means that R/UR/UR/U is nilpotent for every open normal subgroup UUU of RRR, with the subgroup and quotient topologies understood. For a group RRR, the series condition used here means that there exist m∈Nm\in\mathbb Nm∈N and a nondecreasing sequence (Si)i∈N(S_i)_{i\in\mathbb N}(Si​)i∈N​ of normal subgroups of RRR such that S0={1}S_0=\{1\}S0​={1}, Sm=RS_m=RSm​=R, and, for each i<mi<mi<m, some ri∈Rr_i\in Rri​∈R satisfies Si+1=⟨Si,ri⟩S_{i+1}=\langle S_i,r_i\rangleSi+1​=⟨Si​,ri​⟩. Repeated terms are allowed, and m=0m=0m=0 is allowed precisely when RRR is trivial. Saying that RRR is prosupersolvable means that every quotient R/UR/UR/U by an open normal subgroup satisfies this series condition. The normality assumption on N∩HN\cap HN∩H is in NNN, not a requirement of normality in GGG. The local witnesses can vary with ppp, whereas the conclusion concerns one conjugate of the whole subgroup JJJ. All primes are quantified, including those with trivial Sylow subgroups; trivial groups and trivial factors in the unique product decomposition are permitted.

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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