The local (140) residues for G_ℚ₂ #
For the local source Γ = G_ℚ₂ = AbsGalQ2, this file proves the per-source residues consumed by
the source-generic phase140_from_residues in GQ2/Phase140Assembly.lean: hsep,
hpartial, hZcard, and hμ (the T-cocycle count). hGaussZ is supplied separately
(kept as a hypothesis here); htriv/hH2 are discharged locally (htriv_local' /
card_H2_zmod2_eq_two).
#print axioms phase140_local is contained in the standard three axioms together with B6
(tateDualityAt) and B7 (absGalQ2_localEulerCharacteristic). The four residues are
htriv_local', vFixedPts_eq_one, the two counting residues
tcocycle_card_local (the hμ supplier) and hZcard_local; the deep separation residue
hsep_local (7 stages: Additive T module → tDef ∈ Z² → dual/hpair → cup20-bridge with
the χ↔n∈TCharC invariance transport → bijective_cup20 injectivity → B²-extraction → the direct
M-lift f γ = ψγ·fLift γ); and — the last one — the nondegeneracy residue hpartial_local
(contrapositive: ∀c, betaChi χ c = betaChi χ 0 ⟹ split χ∘mDef by gχ → the cup part iotaB-
vanishes → the dual-connecting cochain ξ is a Z¹(Γ, ElemDual V) whose every cup value vanishes
→ [ξ]=0 by cup11 right-slot separation → ξ = ∂n → build the invariant M-character
ψ(m) = χ(t-part m) + (gχ+n)(V-part m) (additive; Y-conjugation-invariant via bb=uσ(cc)·k,
k∈M, M abelian, collapsing to hkey) → ψ = 0 by Half139Local.mchar_conj_invariant_eq_zero
((M∨)^C = 0, Lemma 7.1) → χ = 0, contradiction).
The theorem hZcard_local requires hnt : ∃ g v, g • v ≠ v; the other module hypotheses alone
do not imply this nontriviality condition, as explained in its declaration below.
The four residues follow two common patterns for the local source:
- the counting residues
hμandhZcardmirrorhMcountM_local(GQ2/Half139Local.lean): build the additive𝔽₂-module of the layer (Tresp.V) with theρ'-conjugationAbsGalQ2-action, bridge the crossed cocycles toZ¹_cont, applycard_Z1_eq(5.16 clause (ii), B7), and evaluate thefixedPtsfactor; - the separation residues
hsepandhpartialmirrorhsep_hom_local(GQ2/RStageLocal.lean): the(T^∨)^C-perfectness of theT-obstruction pairing fromprop_5_16cup clauses (vi)/(iv)/(v) + aB²-extraction.
All four are ∀ ρ-parametric over the C-boundary lifts, in exactly the shape
phase140_from_residues consumes; the assembly phase140_local wires them (plus the ledger
hGaussZ) into the RecursionInputs.phase140-field display.
Axiom use: ⊆ {B6, B7} — B6/B7 via card_Z1_eq / card_H2_eq_fixedPts, exactly
as in hMcountM_local/hZcount_local.
The G_ℚ₂-action on 𝔽₂ is trivial (any group action on ZMod 2 fixes both elements).
A self-contained copy of RStageLocal.htriv_local, inlined to keep this leaf's imports lean.
The shared T-module pack #
Both T-layer residues below (tcocycle_card_local and hsep_local) run the same module
setup: the polar radical T ≤ M of a RadicalCoverData is elementary abelian (M abelian and
2-torsion), additivized to an 𝔽₂-space carrying the conjugation action of the coset group
Bg ⧸ M through Quotient.out representatives. The pack is extracted here once (the
mbCommGroup/mbConjActC idiom of MStageCountGammaA); the residues install it by
letI/have and diverge at their count/separation tails.
The T-cocycle count for G_ℚ₂ (the hμ supplier, the Prop. 8.9 assembly): the crossed-T-cocycle
count is the card_Z1_eq closed form #T² · #(T^∨)^{YB/M_B}, which is ρ-independent (the RHS
sees only the frame-level datum En.radData l h, not ρ) — so the capstone reads off μ₀ and
hμ := fun ρ => tcocycle_card_local … ρ. Mirrors hMcountM_local steps 1–3 at
A := Additive (En.radData l h).T, but with a direct TCocycle ≃ Z¹_cont bridge (TCocycle
stores continuity into Bg directly, and is always nonempty — no torsor/Nonempty detour).
No YC-invariant functionals on V: #(V^∨)^{YC} = 1 — the fixedPts factor of the
hZcard card_Z1_eq count. From DualityAssembly.card_fixedPts_elemDual_eq_one_of_nontrivial,
packaging the ledger hsimple/hVne as IsSimpleModTwo RF.YC En.Vmod and the nontrivial action
hnt. (Self-contained; no cocycle bridge needed — the crux of hZcard_local.)
hZcard for G_ℚ₂ — #Z¹_{Γ,ρ'}(V) = #V². Mirrors hMcountM_local at A := En.Vmod
(which already carries the RF.YC-action of the enrichment) with the descent lower map
rho0 = ρ.1.1 (rho0_descData_rhoPrime, surjective since ρ is a ContSurj), building the
VCocycle ≃ Z¹_cont(AbsGalQ2, En.Vmod) bridge and applying card_Z1_eq
(5.16 clause (ii)) to get #V² · #fixedPts RF.YC (ElemDual En.Vmod); the fixedPts factor is 1
by vFixedPts_eq_one. The proof follows the bridge and module-instance setup from
hMcountM_local at A := En.Vmod.
The hypothesis hnt (a nontrivial action) is necessary and is not derivable from
hsimple/hfaith/hVne alone: in the corner #V = 2 ∧ YC = 1 the ledger is satisfiable (𝔽₂ is a faithful — vacuously — simple 𝔽₂[1]-module) yet
#(V^∨)^{YC} = 2 ≠ 1, so hZcard is FALSE there. hnt (equivalently Nontrivial RF.YC, via
hfaith) rules it out and is discharged at the capstone from the block's chief-factor structure
(the ramified regular summand has a nontrivial YC-action).
hsep for G_ℚ₂ — the (T^∨)^C-separation: a V-coordinate with all χ-obstructions
betaChi χ c = 0 is T-liftable. The converse of the generic betaChi_of_tliftable
(VLiftCount.lean); the hsep_hom_local pattern (prop_5_16 cup clause (vi) cup20-bijectivity
B²-extraction) at theT-module through theM-lift obstruction.
Proof outline (mirroring RStageLocal.hsep_hom_local at the T-layer):
- Module.
A := Additive ↥(En.radData l h).Twith therhoPrime-conjugationAbsGalQ2-action, usingtcocycle_card_local's setup (conj_eq_of_mk_eq_T,tCommGroup,actC/actG,hcomp,hsmul,ContinuousSMul,hA₂), same module as the T-count. - T-valued defect cocycle
tDefZ2 : (fun p => Additive.ofMul (tDef S hσ c p)) ∈ Z2 AbsGalQ2 A— extract fromchiDef_mem_Z2'shraw/hsub(VLiftCount.lean:234-252), BEFORE pushing throughχ; theγ•in theZ2identity is conjugation byfLift γ(a rep ofρ'γ, so= actG-action byconj_eq_of_mk_eq_T). - Dual module
ElemDual A+hpair— copyhsep_hom_local:466-486(compHom θ,⊥topology,hpairviahtriv_local'+ElemDual.smul_apply+inv_smul_smul). cup20-values vanish∀ n : H0 AbsGalQ2 (ElemDual A), cup20 (dualEval A) hpair (H2mk … ⟨_,tDefZ2⟩) n = 0:cup20 [tDef] n = H2mk (fun gd => dualEval (tDef gd) ((gd.1*gd.2)•n))(congrArg H2mk, as inhsep_hom_local:hred);n.2-invariance ⟹= H2mk (fun gd => n(tDef gd)) = H2mk (chiDef χ_n c)whereχ_n : ↥(TCharC D) := ⟨fun t => n.1 (Additive.ofMul t), ⟨additivity, conj-inv via θ-surj⟩⟩(thehYinvtransport,hsep_hom_local:493-512); thenhc χ_n : betaChi χ_n c = 0giveschiDef χ_n c ∈ B²(iotaB_eq_zero_iff), soH2mk (chiDef χ_n c) = 0(H2mk_eq_zero_iff).- Class vanishes
H2mk … ⟨_,tDefZ2⟩ = 0via(bijective_cup20_dualEval hA₂ htriv_local' hpair).1(injectivity) +map_zero+AddMonoidHom.extover stage 4. - B²-extraction:
(QuotientAddGroup.eq_zero_iff _).mp+mem_addSubgroupOf⟹ψ : AbsGalQ2 → Acontinuous withdOne ψ = tDef(hsep_hom_local:541-543). - Direct lift (the genuinely NEW part — no
homLift_of_splitfor the abstract-DMLiftslayer):f γ := (Additive.toMul (ψ γ) : Bg) * fLift S c γ; a continuous hom overρ'(dOne ψ = tDefcancels thefLift-defect, exponent-2 kills the sign as in:554-563;ψ ∈ T ⊆ Msomk_M (f γ) = mk_M (fLift γ) = ρ'γ), andmk_T (f γ) = mk_T (fLift γ) = (qOfCocycle c) γ(sinceψ ∈ T) ⟹redTLift f = qOfCocycle c⟹TLiftable. Bespoke ~40 lines.
cup11 right-slot separation (clause (iv), vanishing-detector form): a degree-1
ElemDual-class killed by the evaluation cup against every H¹(A)-class is zero. Mirrors
bijective_cup11_dualEval's internals (cup11_comm slot swap + B6 perfect11 injectivity on
the MuDual side); stated separately because the bijective form detects in the left slot
while hpartial needs the right.
hpartial for G_ℚ₂ — nondegeneracy of the obstruction pairing in the character:
every nonzero χ ∈ (T^∨)^C is detected by some V-coordinate. Cup-duality clauses (iv)/(v) of
prop_5_16.
RECIPE: d(c) := betaChi χ c - betaChi χ 0 is ADDITIVE in c (betaChi_affine,
KeystoneDelta.lean:1172), so the goal ∃ c, d(c) ≠ 0 is "the additive map d : VCocycle → 𝔽₂
is nonzero". d is the cup pairing of χ (as H⁰(ElemDual A), via the stage-4 χ ↔ n
identification of hsep_local) against the class-of-c-defect in H¹/H²; by the perfect
(1,1)/(0,2) pairings (bijective_cup11_dualEval / bijective_cup02_dualEval, clauses (iv)/(v),
LocalLiftingDuality.lean:359/409) a NONZERO χ is detected by some class — i.e. d ≠ 0.
Contrapositive form: if d = 0 (all c give betaChi χ c = betaChi χ 0) then χ = 0 by the
injectivity half of the perfect pairing, contradicting hχ. The ∂-surjectivity (that the
c ↦ defect-class map hits enough of H¹/H² to realize the pairing) is the substantive step,
dual to hsep's bijective_cup20 injectivity. Couples to hsep_local's stage-1–4 infrastructure
(same module A, dual, and χ ↔ n bridge).
The local (140) display #
The RecursionInputs.phase140 field for G_ℚ₂: the source-generic
phase140_from_residues with htriv/hH2 discharged locally and the four per-source residues
supplied by the lemmas above. hGaussZ, μ₀, G0, and the module hypotheses
hsimple/hVne/hnt are supplied by the prop_8_9 assembly in GQ2/Prop89Close.lean.
Paper-tag ledger (auto-generated by paperforge; do not edit) #
- Lemma 7.1 = ⟦lem-simplehead⟧