§5 statements: the two source-specific lifting theories #
The paper's §5 sets up, for a finite lower target C and an elementary 𝔽₂[C]-module A,
the two cochain theories that the §9 induction compares: the finite word complex (30) on the
candidate side, and continuous Galois cohomology on the local side. This file is a thin
umbrella: the content now lives in the GQ2/FoxHeisenberg/ sub-modules imported above
(Basic, Heisenberg, Traced, WildRow, HessianRow), which provide the definition layer
(the complex, the Heisenberg groups, the mixed central coordinate) and the proved
Lemmas/Propositions 5.6, 5.7, 5.8, 5.11, 5.12, 5.13, 5.15, 5.16 together with the
5.17-numerics wiring corollary. The overview below documents the §5 encodings shared by all
the sub-modules.
The §5 objects and their encodings #
- Coefficients.
Ais an "elementary𝔽₂[C]-module":[AddCommGroup A]+[DistribMulAction C A]+ the hypothesishA₂ : ∀ a : A, a + a = 0(+[Finite A]where the paper says finite). NoModule 𝔽₂instances (the continuous-cohomology and Demushkin conventions); "dim"-statements are stated inNat.cardform (e.g.2^{2 dim A + dim (A^∨)^C}becomes#A² · #(A^∨)^C). - The lower map. The complex depends on
ρ : Γ ↠ Conly through the four marked valuesρ(σ), ρ(τ), ρ(x₀), ρ(x₁), i.e. through the pushed markingunivMarking.map ρ— so the whole candidate-side theory is parametrized by at : Marking C(GQ2/Words.lean), keeping §5 purely finite. The relations enter as hypothesest.TameRel,t.WildRelwhere the paper assumesρkills the relators. - Relator values.
Marking.tameValue = τ^σ (τ²)⁻¹andMarking.wildValue = h₀u₁⁻¹x₁^σc₀(relations (5)/(6) as elements;= 1 ↔ TameRel/WildRelproved). Theω₂-powers arepowOmega2— by the profinite-exponentiation API's headline these compute the profiniteω₂in every finite group, and bypowOmega2_pow_eqany integer representative modulo the relevant exponent agrees: that is exactly Lemma 5.1 (finite-exponent independence), which is therefore absorbed by the encoding and not re-stated. A ⋊ C(WordLift A C): own structure with the paper's lift convention(u, g)(v, h) = (u + g•v, gh)(Lemma 5.5's proof display) — definitional, noMultiplicative-wrappedSemidirectProduct(avoids the Demushkin wrapper traps).- The word complex (30)/(31).
d0 t : A →+ (Fin 4 → A)is (31) (indices0,1,2,3=σ,τ,x₀,x₁, matchingunivMarking);d1Fun t xis the pair ofA-coordinates of the two relator values at the lifted markingliftMarking t x— the paper's "coefficient ofAin the evaluated tame and wild relators", verbatim. Additivity ofd1Funis the paper's "finite Fox rules", proved asd1Fun_add(via the ledger of Lemma 5.4); the bundledd1 tis built on it, andZ1w/H0w/H1w/H2wfollow theContCohshape (H1 = Z1 ⧸ B1.addSubgroupOf Z1— total definitions, no chain condition needed; the chain identityd¹∘d⁰ = 0under the relations is the separate provedd1Fun_comp_d0). The proved stress testd1Fun_tamecomputes the tame row in closed form — the general form of display (34), validating the convention stack (lift order,conjP, the(u,g)(v,h)rule) end-to-end. 𝔽₂-duals (ElemDual A := A →+ ZMod 2): the Tate-duality interface'sMuDualdef-synonym recipe (ownFunLike, contragredient action(g•λ)(a) = λ(g⁻¹•a); a plainabbrevwould collide with Mathlib's codomain-action instance).H(A) ⋊ C(HeisLift A C, §5.2): own structure onA × A^∨ × 𝔽₂ × Cwith the paper's multiplication(a,λ,z)(a',λ',z') = (a+a', λ+λ', z+z'+λ(a'))twisted by the diagonalC-action — again definitional.mixedB t x yis the traced mixed central coordinateB_{ρ,A} = β_t + β_wof Prop 5.8 (the sum of the two words'z-coordinates, not thez-coordinate of their product).- Stokes (Lemma 5.7): stated in the paper's general form — ordinary free group
FreeGroup (Fin n)(Mathlib's, not profinite), evaluationstokesEvalviaFreeGroup.lift, mod-2 exponentsexpMod2via the lift toMultiplicative (ZMod 2). The tame relator's exponent vector(0,1,0,0)(Prop 5.8's proof) is proved here for the free-group tame word (expMod2_fgTame); the wild word's vector was the §5 proof layer content (it needs the integer-ω₂representative words) and is proved in the sub-modules. - Duality statements. 5.15/5.16 are stated in
Nat.card+ pairing form; "perfect" is encoded as two-sided nondegeneracy (equivalent to perfectness for finite elementary groups, given the card clauses). On the candidate side the descendedH¹×H¹-pairing is carried inside the statement (∃ P, descends mixedB ∧ nondegenerate) — no descent-backed definitions. On the local side the pairing is the already-descended cup product with the evaluation pairingdualEval, in the form used byTateDuality;TateDualityphrasing; the target-line certification is the clause#H²(𝔽₂-trivial) = 2.IsSelfDualpackages the 5.15 conclusion; Lemma 5.11 (dévissage) is stated as two-out-of-three forIsSelfDualalong a short exact sequence of coefficient modules — the mapping coneK(A)of (49) is its proof device (the §5 proof layer), not statement content (flagged deviation). - Prop 5.10 (the Fox–Heisenberg chain map) is not packaged as a
HomologicalComplexmap: its degree-(0,2) components are the trivialtraceD0/traceD2below, and its two chain identities (47)/(48) are — after unfolding the canonical identifications — exactly Prop 5.8's (41)/(42) withL = d1FunonAresp.A^∨. Statement content = 5.8 + 5.6; deviation flagged.
Encoding deviations #
- Corollary 5.17's adjoint-boundary identity (58) uses connecting maps
∂ : H¹(V) → H²(T)in both theories (snake maps for the word complex, coefficient-SES connecting maps forContCoh). The numerical half iscor_5_17_card; the connecting-map formulation is kept in the downstream assembly where both complexes are available. - Lemmas 5.2/5.3/5.4/5.14 are represented by the class-two identity,
h₀-shadow, ledger, and Hessian calculations in the proof modules. Lemma 5.1 is absorbed into the definitions above.
Conventions: x ^ g = g⁻¹xg (conjP), [x,y] = x⁻¹y⁻¹xy (commP), marking order
(σ, τ, x₀, x₁) = indices 0,1,2,3.