Module

RationalCyclotomicZHatRigidity.lean

Nyll.ClassFieldTheory.GlobalClassFieldTheory.Reciprocity.RationalCyclotomicZHatRigidity
3 declarations indexed from sourceView source ↗

Prime-power detection for the rational cyclotomic ZHat-Artin map

Prime-power reductions of the genuine cyclotomic character detect the full rational cyclotomic automorphism. Restricting that automorphism through actual finite cyclotomic levels then detects every finite coordinate of the rational cyclotomic ZHat-extension.

Declarations

Source context 5 commands

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

open scoped NumberField IsMulCommutative
open NumberField ClassFormation
noncomputable section
namespace GlobalClassFieldTheory
namespace Reciprocity
instance (p : Nat.Primes) : Fact p.1.Prime
GlobalClassFieldTheory.Reciprocity.rationalCyclotomicZHatGlobalArtin_sq_eq_one_of_character_reductions

If all prime-power character reductions of the full cyclotomic global Artin symbol have square one, then the corresponding Artin symbol in the actual rational ZHat-extension has square one.

Source context 6 commands

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

open scoped NumberField IsMulCommutative
open NumberField ClassFormation
noncomputable section
namespace GlobalClassFieldTheory
namespace Reciprocity
local instance (p : Nat.Primes) : Fact p.1.Prime :=
  ⟨p.2⟩
theorem
    rationalCyclotomicZHatGlobalArtin_sq_eq_one_of_character_reductions
    (a : IdeleGroup ℚ)
    (h :
      ∀ (p : Nat.Primes) (k : ℕ),
        Units.map (PadicInt.toZModPow k).toMonoidHom
              (KummerTheory.rationalCyclotomicCharacterPrimeProduct
                (infiniteGlobalArtinMonoidHom
                  ℚ KummerTheory.rationalCyclotomicField a) p) ^ 2 =
          1) :
    rationalCyclotomicZHatGlobalArtin a ^ 2 = 1
GlobalClassFieldTheory.Reciprocity.rationalCyclotomicZHatIdeleValue_eq_one_of_character_reductions

Prime-power square-one identities force the rational cyclotomic idele value itself to be trivial. Torsion-freeness of ZHat removes the residual order-two ambiguity.

Source context 6 commands

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

open scoped NumberField IsMulCommutative
open NumberField ClassFormation
noncomputable section
namespace GlobalClassFieldTheory
namespace Reciprocity
local instance (p : Nat.Primes) : Fact p.1.Prime :=
  ⟨p.2⟩
theorem
    rationalCyclotomicZHatIdeleValue_eq_one_of_character_reductions
    (a : IdeleGroup ℚ)
    (h :
      ∀ (p : Nat.Primes) (k : ℕ),
        Units.map (PadicInt.toZModPow k).toMonoidHom
              (KummerTheory.rationalCyclotomicCharacterPrimeProduct
                (infiniteGlobalArtinMonoidHom
                  ℚ KummerTheory.rationalCyclotomicField a) p) ^ 2 =
          1) :
    rationalCyclotomicZHatIdeleValue a = 1