Documentation

GQ2.Foundations.Axioms

Classical literature inputs for Theorem 1.2 #

Every axiom in the GQ2 library lives in this file, a rule enforced by scripts/check_axioms.sh. Each axiom represents a published mathematical input used by the paper; the paper-specific propositions and theorems are proved elsewhere in the library.

The current census contains nine axioms:

Four interfaces that were formerly axioms are now constructed in the repository under the same names: HilbertSymbol.hilbertSymbol_dyadic, unramifiedQuadratic_units_are_norms, kummerClassK_surjective, and dyadicUnitFiltration. Keeping their public names unchanged lets consumers use the proved implementations without an API migration.

For review, the live leaves fall into three citation-faithfulness classes:

The declaration docstrings below give the precise statement, source citation, paper cross-reference, and any encoding or convention that prevents the Lean statement from being a verbatim transcription of one published theorem. The full dependency table is in docs/literature-axioms.md, matching Appendix D of the paper.

References from the paper bibliography:

[1] Neukirch–Schmidt–Wingberg, Cohomology of Number Fields, 2nd ed., Springer 2015. (NSW) [2] Labute, Classification of Demushkin groups, Canad. J. Math. 19 (1967), 106–132. [3] Serre, Structure de certains pro-p-groupes, Sém. Bourbaki 252 (1962–64). [4] Ribes–Zalesskiĭ, Profinite Groups, 2nd ed., Springer 2010. (RZ) [7] Serre, Local Fields, GTM 67, Springer 1979. [CiA] Serre, A Course in Arithmetic, GTM 7, Springer 1973.

B1 — topological finite generation #

axiom GQ2.Foundations.absGalQ2_isTopologicallyFinitelyGenerated :
∃ (s : Finset AbsGalQ2), (Subgroup.closure s).topologicalClosure =

[Classical — B1.] The absolute Galois group of a p-adic local field is topologically finitely generated (in fact by [K : ℚ_p] + 2 elements). For K = ℚ₂ this is the input hfgG that main_presentation feeds to reconstruction.

Citation: NSW [1], Ch. VII §7.4, Theorem (7.4.1) — for every p-adic local field k, G_k is generated by N+2 elements (N=[k:ℚ_p]). This theorem applies at p=2 and is the direct source for the statement below. Jannsen, Invent. Math. 70 (1982), Satz 3.2 and Lemma 3.3, gives the weaker N+3 bound, which would also suffice. Verified against the cited PDFs; the audit copies are not vendored in this repository.

This is a genuine, faithful Lean statement: it is exactly the topological-finite-generation predicate used throughout Reconstruction.lean. Paper: Lemma 2.5 (the hfgG input to the reconstruction argument).

B7 — the local Euler–Poincaré characteristic #

Statement conventions, citation discussion, and the derived stress tests (finite_H1, card_H1, …) are in GQ2/EulerCharacteristic.lean, which imports this file.

axiom GQ2.Foundations.absGalQ2_localEulerCharacteristic (M : Type u_1) [AddCommGroup M] [TopologicalSpace M] [DiscreteTopology M] [DistribMulAction AbsGalQ2 M] [ContinuousSMul AbsGalQ2 M] [Finite M] :
Finite (ContCoh.H0 AbsGalQ2 M) Finite (ContCoh.H1 AbsGalQ2 M) Finite (ContCoh.H2 AbsGalQ2 M) Nat.card (ContCoh.H1 AbsGalQ2 M) = Nat.card (ContCoh.H0 AbsGalQ2 M) * Nat.card (ContCoh.H2 AbsGalQ2 M) * 2 ^ padicValNat 2 (Nat.card M)

[Classical — B7 (local Euler–Poincaré characteristic).] For every finite discrete G_ℚ₂-module M, the continuous cohomology groups Hⁱ(G_ℚ₂, M) are finite for i = 0, 1, 2, and

#H¹(G_ℚ₂, M) = #H⁰(G_ℚ₂, M) · #H²(G_ℚ₂, M) · 2 ^ v₂(#M).

Equivalently χ := #H⁰ · #H² / #H¹ = ‖#M‖_{ℚ₂} = 2 ^ (−v₂(#M)).

Citation: NSW [1], Ch. VII §7.3, Theorem (7.3.1) (Tate) (χ(k, A) = ‖#A‖_k); Serre, Galois Cohomology, Ch. II §5.7 Theorem 5; Milne, ADT Thm I.2.8. Paper: §9.2, eq. (145). See GQ2/EulerCharacteristic.lean for conventions and for the (retained-for-faithfulness) redundancy of the H⁰-finiteness clause.

B7′ — the dyadic Hilbert-symbol formula #

hilbertSymbol, ε, ω, unit2, unitCoe, signOf and their unconditional theory live in GQ2/HilbertSymbol.lean.

theorem GQ2.HilbertSymbol.hilbertSymbol_dyadic (α β : ) (u v : ℤ_[2]ˣ) :
hilbertSymbol (unit2 ^ α * unitCoe u) (unit2 ^ β * unitCoe v) = signOf (ε u * ε v + α * ω v + β * ω u)

The dyadic Hilbert symbol formula, formerly interface B7′. Writing a = 2^α u, b = 2^β v with u, v ∈ ℤ₂ˣ, the Hilbert symbol over ℚ₂ is (a, b)₂ = (-1)^{ε(u) ε(v) + α ω(v) + β ω(u)}.

Citation: Serre, A Course in Arithmetic [CiA], Ch. III §1.2, Theorem 1 (the p = 2 case), with ε, ω the residue characters of Ch. II §3.3. This is exactly the paper's Lemma 3.5 formula for the cup product on H¹(ℚ₂, μ₂). Convention: signOf sends the 𝔽₂-valued exponent to {±1} = ℤˣ; every element of ℚ₂ˣ has the form 2^α u (α ∈ ℤ, u ∈ ℤ₂ˣ), so this determines the symbol on all of ℚ₂ˣ × ℚ₂ˣ.

The theorem delegates to hilbertSymbol_dyadic' in GQ2/HilbertSymbolDyadicClose.lean, whose proof uses 2-adic Hensel lifting, the norm-form identity (a,b) = (a,−ab), and finite mod-8 computations.

B3c — the canonical dyadic orientation (cyclotomic interface) #

The bundle DyadicOrientation — a B4 isomorphism together with the descended cyclotomic character, normalized to Labute's Theorem 4(2) values on the marked generators — and the route-(ii) decision with its flagged deviations are in GQ2/Orientation.lean; its stress tests are bundle-parametrized and axiom-free.

axiom GQ2.dyadicOrientation [CompactSpace AbsGalQ2] [TotallyDisconnectedSpace AbsGalQ2] :

The B3c axiom (composite interface — Labute [2], Théorème 4, case (2): q = 2, n = 3 odd, f = 2). There is a B4 isomorphism ψ : G_{ℚ₂}(2) ≅ D₀ and a continuous descent χ₂ of the cyclotomic character through G_{ℚ₂} ↠ G_{ℚ₂}(2), surjective (image invariant {±1} × U₂⁽²⁾ = ℤ₂ˣ), with values (χ(A), χ(S), χ(Y)) = (−1, 1, (−3)⁻¹) — the paper's χ_D-row of eq. (13) (Lemmas 3.4/3.5).

Composite classification (docs/adversarial-axioms-review.md §3): this is not a bare Labute citation. It bundles (a) Labute's orientation/classification values, (b) the local-Galois fact that the Demushkin dualizing character equals the cyclotomic character (through this quotient map — Labute Thm 4 does not by itself assert chiCyc-compatibility), and (c) the choice of a normalized B4 isomorphism realizing (a)+(b) on the marked generators. Consequently B3c subsumes a marked version of B4: a downstream declaration whose #print axioms shows dyadicOrientation need not also list B4 in its Ax column unless B4 is consumed independently (the review-packet classification table, docs/orchestration/review-packet.md §2, records this).

Deviation (route (ii), flagged in GQ2/Orientation.lean): the abstract dualizing characterization of the canonical character (Labute Prop. 6) is not formalized; the bundle asserts exactly the interface the paper consumes.

Citation: Labute [2], Théorème 4 case (2) and Théorème 8 (Canad. J. Math. 19 (1967), 106–132); dualizing character = cyclotomic through this quotient: NSW [1], Ch. VII §7.5, (7.5.11)–(7.5.12); Serre [3]. Paper: Lemma 3.4 → Prop. 1.1. docs/literature-axioms.md B3/B3c.

B5 — the local reciprocity bundle #

The bundle structure LocalReciprocity (with the convention table and the soundness note on the profinite target of ν_ur) is defined in GQ2/Reciprocity.lean; its stress tests are parametrized over an arbitrary bundle and are therefore axiom-free.

The B5 axiom. Local class field theory for ℚ₂ provides the reciprocity bundle.

Citation: NSW [1] (7.1.1)/(7.1.5); Serre Local Fields [7] Ch. XI–XIII. Paper: Lemma 3.5, eq. (13); Prop. 1.1.

B6 — local Tate duality (per-n bundle, at every finite k/ℚ₂) #

The dual module MuDual n M = Hom(M, μₙ) (conjugation action), the evaluation cup pairing, the group-parametric bundle TateDualityG G n (with TateDuality n = the G_ℚ₂ member), and the gate IsLocalDualizingGroup — with the encoding decisions and flagged deviations (per-n form, ℤ/n-valued Pontryagin duals, single currying, unnormalized inv) — are defined in GQ2/TateDuality.lean; its stress tests are parametrized over an arbitrary bundle and are therefore axiom-free.

axiom GQ2.tateDualityAt (G : Type) [Group G] [TopologicalSpace G] [IsTopologicalGroup G] (n : ) [NeZero n] [DistribMulAction G (MuN n)] [ContinuousSMul G (MuN n)] (hloc : IsLocalDualizingGroup G n) :

The B6 axiom (base-generalized to all finite k/ℚ₂). Local Tate duality at any local Galois group G over ℚ₂ (G_ℚ₂ or an open finite-index subgroup G_K, K/ℚ₂ finite — the IsLocalDualizingGroup hypothesis): an invariant map inv : H²(G, μₙ) ≃+ ℤ/n making the evaluation cup pairings Hⁱ(G, Hom(M, μₙ)) × H^{2−i}(G, M) → H²(G, μₙ) ≅ ℤ/n perfect for every finite discrete n-torsion G-module M, in the three degree pairs (0,2), (1,1), (2,0).

NSW (7.2.6) states Tate duality for arbitrary p-adic k, so the interface is parametrized by a local dualizing group rather than restricted to ℚ₂. The base member k = ℚ₂ is the in-repository definition GQ2.tateDuality below.

Citation: NSW [1], Ch. VII §7.2, Theorem (7.2.6) (local Tate duality, for any p-adic k); Serre, Galois Cohomology II §5.2, Theorem 2; Milne, ADT I.2.3. Induced mod-2 Hilbert-pairing nondegeneracy over G_K: FV Ch. IV §5 Prop (5.1)(6)/Cor./Thm (5.2), O'Meara ITQF 63:13. Paper: §§5–8 (the 𝔽₂ dimension counts) and §6.3; docs/literature-axioms.md B6, docs/orchestration/p15f7-axiom-proposal.md.

noncomputable def GQ2.tateDuality (n : ) [NeZero n] :

B6 at the base field ℚ₂ — the G = G_ℚ₂ member of tateDualityAt, using isLocalDualizingGroup_absGalQ2.

Equations
Instances For

    B8 — the cyclotomic action on peripheral generators (Lemma 3.6) #

    The concrete group Δ = maxPro2(FreeProfinite (Fin 2)), its peripheral generators P, T, C, and the bundle PeripheralCyclotomicAction — with the flagged faithfulness deviation (the literal statement is about the outer action on an étale/anabelian π₁, absent from Mathlib) and the pinning of the exponent embedding ι — are defined in GQ2/PeripheralAction.lean.

    [Composite — B8.] Local cyclotomic action on the peripheral inertia generators of Δ = π₁^{pro-2}(ℙ¹ ∖ {0,1,∞}): for every u ∈ ℤ₂ˣ there is a continuous automorphism φ_u of Δ sending each peripheral generator to a cyclotomic conjugate, φ_u(P) = c_P⁻¹ · P^u · c_P (and likewise T, C), the u-th power via ẑ-exponentiation. This is Lemma 3.6's group-theoretic conclusion; see GQ2/PeripheralAction.lean for the deviation from the literal π₁ statement.

    This is a composite leaf, not Stix alone (docs/adversarial-axioms-review.md §1). Stix supports that the decomposition group acts on cuspidal inertia through the cyclotomic character; producing an automorphism for every u ∈ ℤ₂ˣ — the aut : ℤ_[2]ˣ → ContinuousMulEquiv Δ Δ field, quantified over all units — additionally needs a cyclotomic-surjectivity input (a decomposition-group element realizing each u). Locally, B5 supplies this through χ_cyc(rec u) = u⁻¹ and dense reciprocity image. B8 keeps the all-units form because that is the interface consumed by Lemma 3.6.

    Citation: Stix [8], §3.3 + Definition 37 (cuspidal inertia acts through the cyclotomic character — the paper's exact citation) together with local cyclotomic surjectivity from B5; classical origin Deligne, MSRI 16 (1989). Paper: Lemma 3.6. docs/literature-axioms.md B8.

    B9 — the Evens/Kahn formula (paper eq. (111)), degrees ≤ 2 #

    The ingredients — degree-1 corestriction corH1Z, the index-two Evens norm evensNormH2Z (the paper's two-point graph cocycle (98), Lemma 6.13), and the subgroup Kummer cocycle kummerZ1On — are all defined (with full well-formedness proofs) in GQ2/EvensKahn.lean; Stiefel–Whitney classes of the rank-2 transfer forms enter through the paper's fixed diagonalizations Tr_{L/k}⟨a⟩ ≃ ⟨2u, 2dn/u⟩, Tr_{L/k}⟨1⟩ ≃ ⟨2, 2d⟩ (Lemma 6.16), with w₁⟨x,y⟩ = [x]+[y] and w₂⟨x,y⟩ = [x]∪[y] in Kummer classes. The axiom asserts the degree-1 and degree-2 components of (111) for these representatives. Deviations (flagged; see GQ2/EvensKahn.lean): truncation to degrees ≤ 2; concrete diagonal representatives (Delzant well-definedness absorbed into the scoping); the degree-1 component is equivalent to the classical cor[a] = [N_{L/k}a] compatibility.

    axiom GQ2.evensKahn_dyadic (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] (u n d : (↥k)ˣ) (v : k) (hn : n = u ^ 2 - d * v ^ 2) (δ β : AlgebraicClosure ℚ_[2]) ( : δ ^ 2 = d) ( : β ^ 2 = u + v * δ) (hβ0 : β 0) (hidx : ((MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup).index = 2) (s : k.fixingSubgroup) (hs : s(MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup) (htriv : ∀ (g : k.fixingSubgroup) (m : ZMod 2), g m = m) (hUo : IsOpen ((MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup)) (α : ((MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup)ZMod 2) (hαdef : ∀ (g : ((MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup)), α g = Kummer.kummerCocycleFun β g) ( : ∀ (g h : ((MulAction.stabilizer (Kummer.GaloisGroup ℚ_[2]) δ).subgroupOf k.fixingSubgroup)), α (g * h) = α g + α h) (hαc : Continuous α) :
    kummerClassK k (twoUnit k * u) + kummerClassK k (twoUnit k * d * n * u⁻¹) = kummerClassK k (twoUnit k) + kummerClassK k (twoUnit k * d) + corH1 htriv hUo hidx hs α hαc ((trivialCupPairing 2 (↥k.fixingSubgroup) htriv) (kummerClassK k (twoUnit k * u))) (kummerClassK k (twoUnit k * d * n * u⁻¹)) = ((trivialCupPairing 2 (↥k.fixingSubgroup) htriv) (kummerClassK k (twoUnit k))) (kummerClassK k (twoUnit k * d)) + ((trivialCupPairing 2 (↥k.fixingSubgroup) htriv) (kummerClassK k (twoUnit k) + kummerClassK k (twoUnit k * d))) (corH1 htriv hUo hidx hs α hαc) + evensNormH2 htriv hUo hidx hs α hαc

    The B9 axiom (Kahn Théorème 2 at rank 1, expanded by Evens Theorem 1 / Kozlowski Thm 1.1 for index 2; paper eq. (111), degrees ≤ 2, at the Lemma 6.16 diagonalizations), over an arbitrary finite dyadic base k.

    Setting: k/ℚ₂ finite (an IntermediateField of the fixed ℚ̄₂, so all classes live over the subtype group G_k = k.fixingSubgroup ≤ G_ℚ₂), L = k(δ) with δ² = d ∈ kˣ, G_L = N = the stabilizer of δ within G_k (assumed of index 2 — i.e. d is a non-square in k), s ∉ N, and a = u + vδ ∈ Lˣ with norm n = u² − dv² ∈ kˣ and a square root β = √a ∈ k̄ˣ. With [x] = kummerClassK k x the base-general Kummer classes (canonical roots, GQ2/EvensKahn.lean), ∪ = trivialCupPairing, cor = corH1 and N^{Ev} = evensNormH2 (the unbundled forms; the Kummer 1-cocycle α(g) = κ_β(g) of a over N enters via its defining equation hαdef, with its hom/continuity side-proofs quantified), the two components of (111) read:

    • degree 1: [2u] + [2dn/u] = [2] + [2d] + cor[a];
    • degree 2: [2u] ∪ [2dn/u] = [2] ∪ [2d] + ([2] + [2d]) ∪ cor[a] + N^{Ev}[a].

    The cited theorems hold over any field of characteristic different from 2 (Kahn Th. 2 requires no local hypothesis), while the paper invokes (111) over the finite dyadic base k of Lemma 6.16. The interface is therefore base-general within the dyadic setting; k = ℚ₂ is the bottom-field instance.

    Citation: Kahn, Invent. Math. 78 (1984), Théorème 2 (with Théorème 1); Kozlowski, Proc. AMS 91 (1984), Thm 1.1; Evens, Trans. AMS 108 (1963), Thm 1. Paper: §6, eq. (111), Lemmas 6.13/6.16. docs/literature-axioms.md B9.

    B10 — the tame quotient of G_ℚ₂ (Iwasawa) #

    The bundle TameQuotientData (closed normal pro-2 W + G_ℚ₂/W ≅ T_tame), the NSW convention notes (arithmetic-vs-geometric Frobenius, σ ↦ σ⁻¹), and the flagged deviation (no ramification theory: W is characterized, not constructed; its maximality — paper Lemma 3.3 — is deliberately not asserted here) are in GQ2/TameQuotient.lean.

    [Classical — B10 (oriented form, B10′).] The tame quotient of G_ℚ₂, oriented against local reciprocity: a closed normal pro-2 subgroup W ≤ G_ℚ₂ (wild inertia) with G_ℚ₂/W ≅ T_tame = ⟨σ, τ ∣ τ^σ = τ²⟩_prof, whose unramified coordinate ν_t matches B5's reciprocity normalization — ν_t(tameF(rec u)) = 1 for units u and ν_t(tameF(rec 2)) = ztwoOne⁻¹ (arithmetic Frobenius, geometric coordinate).

    Citation, existence: NSW [1], Ch. VII §7.5, Theorem (7.5.3) (Iwasawa)G(k_tr|k) is the profinite group on σ, τ with the single relation στσ⁻¹ = τ^q (q = 2); with (7.5.2) (split extension 1 → Ẑ^{(p′)}(1) → G(k_tr|k) → Γ → 1) and G(k̄|k_tr) pro-p (Serre, Local Fields [7], Ch. IV). Citation, orientation clauses: Serre, Local Fields, Ch. XIII §4, Proposition 13 and its corollary (local reciprocity maps units onto inertia and a prime element to Frobenius). Neukirch, Algebraic Number Theory, Ch. V, Theorem (6.2) concerns the higher unit filtration (n > 0), not the n = 0 assertion; use Chap. V, (1.2) / NSW [1] (7.1.2)(i) for units being norms in unramified extensions. (Verified against the cited PDFs; the audit copies are not vendored in this repository. The Frobenius-direction convention σ = geometric and the clause encoding are documented at OrientedTameQuotient in GQ2/TameQuotient.lean.)

    The orientation clauses are part of this interface because they cannot currently be derived from B5 alone without local ramification theory for Field.absoluteGaloisGroup in Mathlib. Paper: Prop. 3.2 local side + Prop. 3.14 / Cor. 3.12 (the "same natural unramified character"). docs/literature-axioms.md B10.

    B11 — the dyadic norm criterion over finite bases #

    Section 6.3 uses the norm criterion and unit-norm surjectivity over arbitrary finite dyadic bases. The interface separates the remaining classical axiom B11a from the spectral-norm convention and the in-repository proof of unramified unit-norm surjectivity. The combined dyadicNormCriterion theorem below preserves the paired interface for consumers:

    Encoding conventions carried over from the pre-split axiom: the "b is a norm from k(√a)" condition is the norm form b = x² − a y² (elementary, no relative field-extension plumbing); unramifiedness by equal norm value groups through the spectral norm on ℚ̄₂ (the GQ2/SectionSix.lean IsDeepUnit/lemma_6_16 convention).

    Note for reviewers: the Steinberg relation [x]∪[1−x] = 0 and [2]∪[−1] = 0 used in Lemma 6.16's proof are consequences of the criterion clause (norm representations 1 − x = 1² − x·1² and −1 = 1² − 2·1²), so they are deliberately not separate clauses.

    Citation: Serre, Local Fields [7], Ch. XIV §2, Proposition 4(iii) (the symbol–norm criterion; over ℚ_p also CiA [CiA] Ch. III §1.1 Prop. 1), and Ch. V §2 (norms of unramified extensions are the units times the norms of uniformizers). Paper: §6.3, displays (93)/(94) and Lemma 6.16.

    def GQ2.IsUnramifiedQuadraticSpectral (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) (δa : AlgebraicClosure ℚ_[2]) :

    Project convention — isolated spectral-norm bridge. The repo's working definition of "k(δa)/k is unramified", encoded via the spectral norm on ℚ̄₂: every nonzero z = x + y·δa (x, y ∈ k) has the same norm as some nonzero element of the base k — i.e. k(δa) and k have equal norm value groups. This is not a Mathlib unramifiedness notion and is asserted by nothing (it is a def, not an axiom); it is the convention the §6 ledger consumes, named and isolated per adversarial review rec 2 so a human reviewer can see exactly where the project departs from a directly citable statement.

    Equations
    • GQ2.IsUnramifiedQuadraticSpectral k δa = ∀ (z : AlgebraicClosure ℚ_[2]), z 0(∃ (x : k) (y : k), z = x + y * δa)∃ (w : k), w 0 z = w
    Instances For
      axiom GQ2.hilbertSymbol_normCriterion_finiteDyadic (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] (htriv : ∀ (g : k.fixingSubgroup) (m : ZMod 2), g m = m) (a b : (↥k)ˣ) :
      ((trivialCupPairing 2 (↥k.fixingSubgroup) htriv) (kummerClassK k a)) (kummerClassK k b) = 0 ∃ (x : k) (y : k), b = x ^ 2 - a * y ^ 2

      [Classical — B11a.] The dyadic Hilbert-symbol norm criterion over a finite base k/ℚ₂, in Kummer-cup form: for a, b ∈ kˣ, [a] ∪ [b] = 0 in H²(G_k, 𝔽₂) iff b is a norm from k(√a) — iff b = x² − a y² has a solution in k (for a a square the norm form is universal, so no non-square hypothesis is needed).

      Citation: Serre, Local Fields [7], Ch. XIV §2, Proposition 4(iii) (symbol vanishes iff the second entry is a norm), Proposition 5 (the symbol is the cup product), and Proposition 7(iii) (the multiplicative-root-of-unity form); over ℚ_p also CiA Ch. III §1.1 Prop. 1. Paper: §6.3 (norm-criterion input to the local square-class calculation).

      theorem GQ2.unramifiedQuadratic_units_are_norms (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] (a : (↥k)ˣ) (δa : AlgebraicClosure ℚ_[2]) (hδa : δa ^ 2 = a) (hunram : IsUnramifiedQuadraticSpectral k δa) (u : (↥k)ˣ) :
      u = 1∃ (x : k) (y : k), u = x ^ 2 - a * y ^ 2

      Unramified unit-norm surjectivity, formerly interface B11b. If k(√a)/k is unramified (the IsUnramifiedQuadraticSpectral convention on a chosen root δa, δa² = a), then every unit of k (‖u‖ = 1) is a norm from k(√a) — i.e. u = x² − a y² is solvable in k.

      Citation: Serre, Local Fields [7], Ch. V §2 (norms of unramified extensions are the units times the norms of uniformizers). Paper: §6.3 (unramified-norm input to the local calculation).

      The proof in GQ2/UnramifiedQuadraticNorms.lean completes the square using the involution σδ = −δ, then constructs a depth-by-depth norm-form approximation wₙ₊₁ = wₙ(1 + πⁿ⁺¹z₀) against the dyadic unit filtration. Exact trace coverage z ↦ z + σz supplies each increment.

      theorem GQ2.dyadicNormCriterion (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] (htriv : ∀ (g : k.fixingSubgroup) (m : ZMod 2), g m = m) :
      (∀ (a b : (↥k)ˣ), ((trivialCupPairing 2 (↥k.fixingSubgroup) htriv) (kummerClassK k a)) (kummerClassK k b) = 0 ∃ (x : k) (y : k), b = x ^ 2 - a * y ^ 2) ∀ (a : (↥k)ˣ) (δa : AlgebraicClosure ℚ_[2]), δa ^ 2 = a(∀ (z : AlgebraicClosure ℚ_[2]), z 0(∃ (x : k) (y : k), z = x + y * δa)∃ (w : k), w 0 z = w)∀ (u : (↥k)ˣ), u = 1∃ (x : k) (y : k), u = x ^ 2 - a * y ^ 2

      The combined dyadic norm criterion. This theorem pairs the classical B11a leaf with the proved unramified-unit theorem. The spectral-unramifiedness convention remains isolated in IsUnramifiedQuadraticSpectral, which is a definition rather than an axiom.

      In-repository Kummer and unit-filtration interfaces #

      Lemma 6.17 uses local Kummer surjectivity and the graded structure of the dyadic unit filtration. Both interfaces are constructed below from in-repository proofs. The surrounding DeepKummerData assembly is developed in GQ2/LocalKummer.lean; its remaining inputs include coprime averaging, the Hensel square criterion, graded duality, Lemma 6.10, and Lemma 6.11.

      theorem GQ2.kummerClassK_surjective (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] :
      Function.Surjective (kummerClassK k)

      Local Kummer theory, surjective half, formerly interface B12.

      For a finite extension k/ℚ₂, the Kummer class map descends to an isomorphism k^×/(k^×)² ≅ H¹(G_k, ℤ/2) (continuous cochain cohomology; μ₂ ≅ ℤ/2, canonical in char 0). This theorem exposes only surjectivity; injectivity is proved separately by Kummer.kummerClass_eq_zero_iff ([a] = 0 ↔ IsSquare a) via Mathlib's infinite Galois correspondence.

      Citation: NSW [1], Ch. VI §2 — Theorem (6.2.1) (Hilbert's Satz 90) and the Kummer-sequence isomorphism H¹(G_K, μ_n) ≅ K^×/K^{×n} displayed immediately after it (electronic ed. p. 344), dual form Theorem (6.2.2); at n = 2. Secondary: Serre, Local Fields [7], Ch. XIV §2 (p. 206). Both verified verbatim against the cited PDFs; the audit copies are not vendored in this repository.

      The proof in GQ2/KummerSurjectivity.lean combines completing the square with the Krull–Galois correspondence from GQ2/KummerKrullBridge.lean, where an open index-two subgroup produces the required quadratic subextension.

      Paper: §6.3 (Lemma 6.17, "By Hochschild–Serre and Kummer theory"). docs/literature-axioms.md B12.

      noncomputable def GQ2.dyadicUnitFiltration (k : IntermediateField ℚ_[2] (AlgebraicClosure ℚ_[2])) [FiniteDimensional ℚ_[2] k] :

      The dyadic unit filtration interface, formerly B13.

      Every finite extension k/ℚ₂ carries a DyadicUnitFiltration (GQ2/UnitFiltration.lean): a uniformizer π (an element of maximal spectral norm < 1 — discreteness of the value group), the normalization ‖2‖ = ‖π‖^e (e = v_k(2) ≥ 1), a residue degree f ≥ 1, and the graded counts of the unit filtration U^{(i)} = 1 + 𝔭_k^i: #(U^{(0)}/U^{(1)}) = 2^f − 1 and #(U^{(i)}/U^{(i+1)}) = 2^f for i ≥ 1.

      Citation: Serre, Local Fields [7], Ch. IV §2, Proposition 6 (verified verbatim against the cited source, pp. 66–67; the audit copy is not vendored): "(a) U_L/U_L^{(1)} = L̄^*; (b) for i ≥ 1, the group U^{(i)}/U^{(i+1)} is canonically isomorphic to 𝔭_L^i/𝔭_L^{i+1}, which is itself isomorphic (non-canonically) to the additive group of the residue field " — read through #L̄ = 2^f, #L̄^× = 2^f − 1. Uniformizer existence: Serre LF Ch. I–II (discrete valuations, complete fields; standard).

      Deviations (flagged, review-packet §3): stated in spectral-norm vocabulary (no valuation ring/residue field is constructed — the graded pieces enter through their cardinalities, the form the multiplicity count consumes); the proposal's (F2) inertia-twist clause (θ_g = (g•π)/π acting on gr_j by θ_g^j) is derivable from the exact ℚ̄₂-algebra action and the he normalization, so it is deliberately not stored as a field.

      Paper: §6.3, eq. (93) (the display's own bracket "[7, Ch. XIV §§2–3]" is coarse — the filtration is Ch. IV §2). docs/literature-axioms.md B13.

      The definition delegates to dyadicUnitFiltration' in GQ2/UnitFiltrationCounts.lean, built on GQ2/UnitFiltrationTop.lean; Classical.choice selects witnesses from the proved existence lemmas. The uniformizer comes from compactness of the unit ball + an O/2O pigeonhole (no spectral-norm value formula); the residue field O/𝔪 is the finite quotient of the valuation subring; and the graded counts are the explicit isomorphisms U^{(0)}/U^{(1)} ≅ (O/𝔪)ˣ and U^{(i)}/U^{(i+1)} ≅ (O/𝔪)⁺.

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