Module

FiniteIdealTameOrder.lean

Nyll.EtaleFundamentalGroups.Inertia.FiniteIdealTameOrder
5 declarations indexed from sourceView source ↗

Tame and wild orders at an original prime

Defines the finite tame and principal-unit kernel orders and factors the inertia cardinality. Establishes positivity and residue-field invertibility of the tame order.

Declarations

EtaleFundamentalGroups.Inertia.finiteIdealTameOrder

The actual finite tame degree at the original normalization prime. Its local DVR and stabilizer action are constructed from that original prime.

Source context 8 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 v
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
variable (G : Type v) [Group G] [MulSemiringAction G B]
variable (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
def finiteIdealTameOrder : ℕ
EtaleFundamentalGroups.Inertia.finiteIdealWildOrder

The actual principal-unit kernel order at that same original prime.

Source context 8 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 v
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
variable (G : Type v) [Group G] [MulSemiringAction G B]
variable (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
def finiteIdealWildOrder : ℕ
EtaleFundamentalGroups.Inertia.finiteIdealInertia_card_eq_tame_mul_wild

The original ideal-inertia order is the product of the actual tame order and actual principal-unit kernel order. No residue field is opened here.

Source context 8 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 v
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
variable (G : Type v) [Group G] [MulSemiringAction G B]
variable (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealInertia_card_eq_tame_mul_wild :
    Nat.card (Q.inertia G) = finiteIdealTameOrder B G Q hQ * finiteIdealWildOrder B G Q hQ
EtaleFundamentalGroups.Inertia.finiteIdealTameOrder_pos
Source context 8 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 v
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
variable (G : Type v) [Group G] [MulSemiringAction G B]
variable (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealTameOrder_pos [Finite G] : 0 < finiteIdealTameOrder B G Q hQ
EtaleFundamentalGroups.Inertia.finiteIdealTameOrder_isUnit

The actual degree at the original prime is invertible in its actual local residue field.

Source context 8 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 v
variable (B : Type u) [CommRing B] [IsDedekindDomain B]
variable (G : Type v) [Group G] [MulSemiringAction G B]
variable (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
theorem finiteIdealTameOrder_isUnit [Finite G] :
    IsUnit (finiteIdealTameOrder B G Q hQ : IsLocalRing.ResidueField (Localization.AtPrime Q))