Module

IdealLocalizationValuationEquiv.lean

Nyll.SchemeTheory.RingTheory.Ramification.IdealLocalizationValuationEquiv
5 declarations indexed from sourceView source ↗

Prime localization and its valuation-ring model

Constructs the canonical ring equivalence between a Dedekind prime localization and its valuation-ring model in the fraction field. Computation lemmas identify its values on the original coefficients.

Declarations

TameAbhyankar.SGA1.idealLocalizationValuationAlgebra
Source context 4 commands

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

noncomputable section
namespace TameAbhyankar.SGA1
universe u v
variable (B : Type u) (L : Type v) [CommRing B] [IsDedekindDomain B]
    [Field L] [Algebra B L] [IsFractionRing B L]
    (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
instance idealLocalizationValuationAlgebra :
    Algebra B (idealLocalizationValuationSubring B L Q hQ)
TameAbhyankar.SGA1.idealLocalizationValuation_isLocalization
Source context 5 commands

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

noncomputable section
namespace TameAbhyankar.SGA1
universe u v
variable (B : Type u) (L : Type v) [CommRing B] [IsDedekindDomain B]
    [Field L] [Algebra B L] [IsFractionRing B L]
    (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
local instance idealLocalizationValuationAlgebra :
    Algebra B (idealLocalizationValuationSubring B L Q hQ) := by
  change Algebra B (idealLocalizationSubalgebra B L Q)
  infer_instance
theorem idealLocalizationValuation_isLocalization :
    IsLocalization.AtPrime (idealLocalizationValuationSubring B L Q hQ) Q
TameAbhyankar.SGA1.primeLocalizationEquivValuation

The canonical identity-on-coefficients equivalence from the literal prime localization to the already constructed native local valuation ring.

Source context 5 commands

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

noncomputable section
namespace TameAbhyankar.SGA1
universe u v
variable (B : Type u) (L : Type v) [CommRing B] [IsDedekindDomain B]
    [Field L] [Algebra B L] [IsFractionRing B L]
    (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
local instance idealLocalizationValuationAlgebra :
    Algebra B (idealLocalizationValuationSubring B L Q hQ) := by
  change Algebra B (idealLocalizationSubalgebra B L Q)
  infer_instance
def primeLocalizationEquivValuation :
    Localization.AtPrime Q ≃+* idealLocalizationValuationSubring B L Q hQ
TameAbhyankar.SGA1.primeLocalizationEquivValuation_algebraMap

The constructed equivalence uses the actual original normalization coefficient map.

Source context 5 commands

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

noncomputable section
namespace TameAbhyankar.SGA1
universe u v
variable (B : Type u) (L : Type v) [CommRing B] [IsDedekindDomain B]
    [Field L] [Algebra B L] [IsFractionRing B L]
    (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
local instance idealLocalizationValuationAlgebra :
    Algebra B (idealLocalizationValuationSubring B L Q hQ) := by
  change Algebra B (idealLocalizationSubalgebra B L Q)
  infer_instance
theorem primeLocalizationEquivValuation_algebraMap (b : B) :
    primeLocalizationEquivValuation B L Q hQ
        (algebraMap B (Localization.AtPrime Q) b) =
      algebraMap B (idealLocalizationValuationSubring B L Q hQ) b
TameAbhyankar.SGA1.primeLocalizationEquivValuation_algebraMap_coe

The canonical equivalence followed by the actual field inclusion is the original B-coefficient map. Its interface opens no B-action on the target V.

Source context 5 commands

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

noncomputable section
namespace TameAbhyankar.SGA1
universe u v
variable (B : Type u) (L : Type v) [CommRing B] [IsDedekindDomain B]
    [Field L] [Algebra B L] [IsFractionRing B L]
    (Q : Ideal B) [Q.IsPrime] (hQ : Q ≠ ⊥)
local instance idealLocalizationValuationAlgebra :
    Algebra B (idealLocalizationValuationSubring B L Q hQ) := by
  change Algebra B (idealLocalizationSubalgebra B L Q)
  infer_instance
theorem primeLocalizationEquivValuation_algebraMap_coe (b : B) :
    (primeLocalizationEquivValuation B L Q hQ
      (algebraMap B (Localization.AtPrime Q) b) : L) = algebraMap B L b