Module

FiniteIdealNormalizationPower.lean

Nyll.EtaleFundamentalGroups.Inertia.FiniteIdealNormalizationPower
1 declaration indexed from sourceView source ↗

Characteristic powers in tame normalization

Derives that the finite normalization exponent is a power of the residue exponential characteristic using wild-order and inertia-cardinality formulas.

Declarations

EtaleFundamentalGroups.Inertia.finiteIdealNormalizationExponent_exists_expChar_pow

The actual e/n exponent is a power of the actual residue exponential characteristic, derived from the same principal-unit wild group and both original inertia-cardinality formulas. No power assertion is an input.

Source context 3 commands

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

namespace EtaleFundamentalGroups.Inertia
open RamificationTheory.HilbertRamification
universe u v
theorem finiteIdealNormalizationExponent_exists_expChar_pow
    (A : Type u) (B : Type v)
    [CommRing A] [IsDomain A] [IsDiscreteValuationRing A]
    [CommRing B] [IsDedekindDomain B] [Algebra A B]
    [Module.Finite A B] [Module.IsTorsionFree A B]
    [IsGaloisGroup (B ≃ₐ[A] B) A B]
    (Q : Ideal B) [Q.IsMaximal] [Q.LiesOver (IsLocalRing.maximalIdeal A)] (hQ : Q ≠ ⊥) :
    ∃ a : ℕ, finiteIdealNormalizationExponent A B (B ≃ₐ[A] B) Q hQ =
      (ringExpChar Q.ResidueField) ^ a