Module

RingTameCharacterProperties.lean

Nyll.ValuedFieldTheory.Ramification.HilbertRamification.RingTameCharacterProperties
2 declarations indexed from sourceView source ↗

Uniformizer and conjugation formulas for tame characters

Computes powers of the tame character using any uniformizer and proves their compatibility with conjugation and the residue-field action.

Declarations

RamificationTheory.HilbertRamification.DiscreteValuationRing.tameCharacter_pow_eq_uniformizer

Every power of the actual tame character is computed using any uniformizer. In particular this applies to the original e/n exponent.

Source context 6 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
attribute [local instance] maximalIdeal_inertia_normal
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
  (G : Type v) [Group G] [Finite G] [MulSemiringAction G R]
theorem tameCharacter_pow_eq_uniformizer
    (m : ℕ) (π : R) (hπ : Irreducible π)
    (σ : (maximalIdeal R).inertia G) :
    (((tameCharacter R G).toFun σ) ^ m).val.val =
      (residue R (uniformizerRatioUnit R G π hπ σ.val).val) ^ m
RamificationTheory.HilbertRamification.DiscreteValuationRing.tameCharacter_pow_conj

The actual finite root character, with the same normalization power on both sides, intertwines group conjugation and the standard residue action.

Source context 6 commands

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

noncomputable section
namespace RamificationTheory.HilbertRamification.DiscreteValuationRing
open IsLocalRing
universe u v
attribute [local instance] maximalIdeal_inertia_normal
variable (R : Type u) [CommRing R] [IsDomain R] [IsDiscreteValuationRing R]
  (G : Type v) [Group G] [Finite G] [MulSemiringAction G R]
theorem tameCharacter_pow_conj
    (m : ℕ) (g : G) (σ : (maximalIdeal R).inertia G) :
    ((tameCharacter R G).toFun
        (((MulAut.conjNormal (H := (maximalIdeal R).inertia G)).toFun g).toFun σ)) ^ m =
      (restrictRootsOfUnity (MulSemiringAction.toRingHom G (ResidueField R) g)
        (tameOrder R G)).toFun (((tameCharacter R G).toFun σ) ^ m)