Module

LocalHilbertPairingExponentCompatibility.lean

Nyll.ClassFieldTheory.Theorems.HilbertSymbols.LocalHilbertPairingExponentCompatibility
1 declaration indexed from sourceView source ↗

Compatibility of Hilbert pairings at divisible exponents

Pairings constructed from the same arithmetic local Artin maps can be chosen compatibly when m ∣ n. Their values are compared in Kˣ, since they belong to different roots-of-unity subgroups. The public norm criterion places the radical in the first argument. With that convention, the root-quotient formula for arithmetic Artin has an inverse; the inverse occurs on both sides of the exponent comparison and does not change the formula below.

Declarations

ClassFieldTheory.exists_compatibleLocalHilbertPairings_of_dvd

For m ∣ n, there are local Hilbert pairings at exponents m and n whose values satisfy (a,b)ₘ = (a,b)ₙ ^ (n/m) in the base-field unit group. Neither pairing is asserted to be determined by the algebraic laws alone.

Source context 3 commands

Surrounding namespaces, section variables, and local commands at this declaration.

noncomputable section
namespace ClassFieldTheory
universe u
theorem exists_compatibleLocalHilbertPairings_of_dvd
    (K : Type u) [Field K] [ValuativeRel K] [TopologicalSpace K]
    [IsNonarchimedeanLocalField K]
    (m n : ℕ+) (hnK : ((n : ℕ) : K) ≠ 0)
    (hmuN : (primitiveRoots (n : ℕ) K).Nonempty)
    (hmn : (m : ℕ) ∣ (n : ℕ)) :
    ∃ Bm : HilbertPairing K m,
      HilbertPairing.IsLocalHilbertPairing Bm ∧
      ∃ Bn : HilbertPairing K n,
        HilbertPairing.IsLocalHilbertPairing Bn ∧
        ∀ a b : Kˣ,
          (Bm (powerClass K m a) (powerClass K m b)).1 =
            (Bn (powerClass K n a) (powerClass K n b)).1 ^
              ((n : ℕ) / (m : ℕ))