Module

FiniteIdealTameExactness.lean

Nyll.EtaleFundamentalGroups.Inertia.FiniteIdealTameExactness
4 declarations indexed from sourceView source ↗

Wild kernels of finite ideal tame characters

Transports the principal-unit wild subgroup to original ideal inertia and computes its cardinality. Proves surjectivity and the kernel formula for the finite tame character.

Declarations

EtaleFundamentalGroups.Inertia.finiteIdealWildSubgroup

The actual original finite wild subgroup, transported from the SAME principal-unit kernel along the literal inertia identification.

Source context 6 commands

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

noncomputable section
open scoped Pointwise
namespace EtaleFundamentalGroups.Inertia
open RamificationTheory.HilbertRamification.DiscreteValuationRing
universe u
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
  (G : Type u) [Group G] [MulSemiringAction G B]
  (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
def finiteIdealWildSubgroup : Subgroup (idealInertiaGroupObject B G Q)
EtaleFundamentalGroups.Inertia.finiteIdealWildSubgroup_card

The transported wild subgroup has exactly the already computed original wild order.

Source context 6 commands

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

noncomputable section
open scoped Pointwise
namespace EtaleFundamentalGroups.Inertia
open RamificationTheory.HilbertRamification.DiscreteValuationRing
universe u
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
  (G : Type u) [Group G] [MulSemiringAction G B]
  (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealWildSubgroup_card :
    Nat.card (finiteIdealWildSubgroup B G Q hQ) = finiteIdealWildOrder B G Q hQ
EtaleFundamentalGroups.Inertia.finiteIdealTameCharacterGroupMap_surjective

The raw actual original finite character is onto its full root group.

Source context 6 commands

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

noncomputable section
open scoped Pointwise
namespace EtaleFundamentalGroups.Inertia
open RamificationTheory.HilbertRamification.DiscreteValuationRing
universe u
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
  (G : Type u) [Group G] [MulSemiringAction G B]
  (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealTameCharacterGroupMap_surjective [Finite G] :
    Function.Surjective (finiteIdealTameCharacterGroupMap B G Q hQ).toFun
EtaleFundamentalGroups.Inertia.finiteIdealTameCharacterGroupMap_ker

Its original-domain kernel is precisely that same transported principal-unit subgroup.

Source context 6 commands

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

noncomputable section
open scoped Pointwise
namespace EtaleFundamentalGroups.Inertia
open RamificationTheory.HilbertRamification.DiscreteValuationRing
universe u
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
  (G : Type u) [Group G] [MulSemiringAction G B]
  (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealTameCharacterGroupMap_ker [Finite G] :
    (finiteIdealTameCharacterGroupMap B G Q hQ).ker = finiteIdealWildSubgroup B G Q hQ