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GQ2.Block.Enrichment

§9 concrete block enrichment — SectionNine.blockEnrichment #

Assembles (blockFrame T Blk hE2).Enrichment from the descent (GQ2/BlockDescent.lean), the form fields (GQ2/BlockFormFields.lean), and the κ⁰ base-class datum. Placed in a separate module (under namespace SectionNine, preserving the FQN SectionNine.blockEnrichment) because it consumes SectionNine.kappa0_exists/ActsThroughTame, so it must sit downstream of GQ2.SectionNine. The two substantive pieces use only the standard axioms:

dat/hdat come from blockKappa0 (= kappa0_exists). The signature takes F : BoundaryFrame H E (cH := F.alpha, hcH := F.alpha_surjective for prop_7_4, and the tame generators F.alpha tameSigma/tameTau for htame).

instance GQ2.SectionNine.blockLY_normal {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) :
T.LY.Normal

L_Y ◁ Y (the marked normal subgroup), as an instance for Y ⧸ T.LY.

hsimple : V = P/S is a simple 𝔽₂[Y/K]-module #

theorem GQ2.SectionNine.blockPS_exp2 {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] (v : Additive (Blk.P Blk.S.subgroupOf Blk.P)) :
v + v = 0

V = P/S is exponent 2: every element has a K-representative k, and k² ∈ R ≤ S.

theorem GQ2.SectionNine.blockHsimple {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] :
FoxH.IsSimpleModTwo (Y Blk.K) (Additive (Blk.P Blk.S.subgroupOf Blk.P))

hsimple: V = P/S is a simple 𝔽₂[Y/K]-module (nontrivial; the only Y/K-stable AddSubgroups are /, by Blk.chief under the subgroup correspondence).

theorem GQ2.SectionNine.blockHnt {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] :
∃ (g : Y Blk.K) (v : Additive (Blk.P Blk.S.subgroupOf Blk.P)), g v v

hnt: the Y/K-action on V = P/S is nontrivial — the enrichment-module form of the block's nontrivial_action field. Only nontriviality is assumed: faithfulness is not block-derivable (a central 2-part of Y outside K centralizes V), but the capstone only consumed hfaith through hnt.) The moving pair is (⟦y⟧_K, ⟦p⟧_S): ⟦y⟧•⟦p⟧ = ⟦p⟧ would put y p y⁻¹ p⁻¹ ∈ S (conjugating the coset relation by p), against nontrivial_action.

htame : the Y/K-action factors through the tame head H #

theorem GQ2.SectionNine.blockLY_smul_eqY {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] (l : Y) (hl : l T.LY) (v : Additive (Blk.P Blk.S.subgroupOf Blk.P)) :
l v = v

L_Y acts trivially on V: L_Y/K is a normal 2-subgroup of Y/K acting on the simple module V, hence trivial by FoxH.lemma_5_12; pull back to the Y-conjugation action.

@[reducible]
noncomputable def GQ2.SectionNine.blockActLY {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] :
DistribMulAction (Y T.LY) (Additive (Blk.P Blk.S.subgroupOf Blk.P))

The descended Y/L_Y-action on VblockActVY descends because L_Y acts trivially (blockLY_smul_eqY); mirrors blockActV's descent through Y/K.

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    theorem GQ2.SectionNine.blockActLY_mk' {H E : Type} [Group H] [CommGroup E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] (y : Y) (v : Additive (Blk.P Blk.S.subgroupOf Blk.P)) :
    (QuotientGroup.mk' T.LY) y v = y v

    Y/L_Y-action on mk' L_Y y reduces to the Y-conjugation action of y.

    theorem GQ2.SectionNine.blockHtame {H E : Type} [Group H] [TopologicalSpace H] [DiscreteTopology H] [Finite H] [CommGroup E] [TopologicalSpace E] [DiscreteTopology E] [Finite E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] (F : BoundaryFrame H E) :
    ActsThroughTame (Y Blk.K) (Additive (Blk.P Blk.S.subgroupOf Blk.P))

    htame: the Y/K-action on V factors through the tame head H (α : Ttame ↠ H); the action descends Y/K ↠ Y/L_Y ≅ H, generators α σ, α τ satisfy the tame relation.

    dat/hdat and the final assembly #

    noncomputable def GQ2.SectionNine.blockKappa0 {H E : Type} [Group H] [TopologicalSpace H] [DiscreteTopology H] [Finite H] [CommGroup E] [TopologicalSpace E] [DiscreteTopology E] [Finite E] {Y : Type} [Group Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] (F : BoundaryFrame H E) (l : BlockDR T Blk) (hlne : l Blk.frattiniK) :
    ∃ (dat : FactorSet (Y Blk.K) (Additive (Blk.P Blk.S.subgroupOf Blk.P))), IsEquivariantFactorSet (blockQbar T Blk F.alpha l hlne) dat

    The κ⁰ base-class datum for q̄_λ, from the proved kappa0_exists (Lemma 6.3), discharging its hsimple/htame hypotheses via blockHsimple/blockHtame.

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      noncomputable def GQ2.SectionNine.blockEnrichment {H E : Type} [Group H] [TopologicalSpace H] [DiscreteTopology H] [Finite H] [CommGroup E] [TopologicalSpace E] [DiscreteTopology E] [Finite E] {Y : Type} [Group Y] [TopologicalSpace Y] [DiscreteTopology Y] [Finite Y] (T : MarkedTarget H E Y) (Blk : SectionSeven.MinimalBlock T.LY) (hE2 : ∀ (e : E), e ^ 2 = 1) [Blk.frattiniK.Normal] [(Blk.S.subgroupOf Blk.P).Normal] [Blk.K.Normal] (F : BoundaryFrame H E) :

      The concrete block enrichment (the §9 induction): the full RF.Enrichment record assembled from the §9 induction descent (blockDescend*/blockActV), the §9 induction form fields (blockQ/blockQbar/…), and the κ⁰ datum (blockKappa0). Takes the boundary frame F (supplying cH := F.alpha for prop_7_4 and the tame generators for htame). Axiom-clean modulo kappa0_exists (the §9 induction).

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