Module

HilbertFiniteFactorNaturality.lean

Nyll.ClassFieldTheory.GlobalClassFieldTheory.Reciprocity.HilbertFiniteFactorNaturality
1 declaration indexed from sourceView source ↗

Naturality of the finite Hilbert factor

The factor obtained by evaluating a local pairing on global units commutes with equivalences of both the number fields and their completions. The commuting square for the two field embeddings is the only geometric input.

Declarations

ClassFieldTheory.globalHilbertPairingFamily_finiteFactor_congr

Transporting a local Hilbert pairing through a compatible equivalence of completions transports its finite factor through the equivalence of global roots of unity.

Source context 5 commands

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

open scoped NumberField
open NumberField IsDedekindDomain
noncomputable section
namespace ClassFieldTheory
universe u v
theorem globalHilbertPairingFamily_finiteFactor_congr
    {F : Type u} {G : Type v}
    [Field F] [NumberField F] [Field G] [NumberField G]
    (e : F ≃+* G) (n : ℕ+)
    (hmuF : (primitiveRoots (n : ℕ) F).Nonempty)
    (hmuG : (primitiveRoots (n : ℕ) G).Nonempty)
    (v : HeightOneSpectrum (𝓞 F)) (W : HeightOneSpectrum (𝓞 G))
    (ec : v.adicCompletion F ≃+* W.adicCompletion G)
    (hcomm : ∀ x : F,
      ec (algebraMap F (v.adicCompletion F) x) =
        algebraMap G (W.adicCompletion G) (e x))
    (hmuC : (primitiveRoots (n : ℕ) (v.adicCompletion F)).Nonempty)
    (BF : GlobalHilbertPairingFamily F n)
    (BG : GlobalHilbertPairingFamily G n)
    (hB : BG W = hilbertPairingOfRingEquiv ec n hmuC (BF v))
    (a b : Fˣ) :
    rootsOfUnityEquivOfRingEquiv e n hmuF
        (GlobalHilbertPairingFamily.finiteFactor F BF hmuF v a b) =
      GlobalHilbertPairingFamily.finiteFactor G BG hmuG W
        (Units.mapEquiv e.toMulEquiv a)
        (Units.mapEquiv e.toMulEquiv b)