Module

SmallActual.lean

Nyll.ClassFieldTheory.GlobalClassFieldTheory.GlobalClassFields.HilbertClassFieldReciprocity.SmallActual
6 declarations indexed from sourceView source ↗

Small Hilbert reciprocity over the realized base field

This leaf specializes the shared reciprocity transport to the actual base field of the selected small Hilbert class field.

Declarations

GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
Source context 7 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F)
GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassField_ideleClassNorm_range_eq_intrinsic

The actual norm range of the selected small Hilbert class field is the intrinsic small-Hilbert norm subgroup of its actual base field.

Source context 8 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem smallHilbertClassField_ideleClassNorm_range_eq_intrinsic :
    (_root_.ideleClassNorm
      (smallHilbertClassFieldBase K)
      (smallHilbertClassField K)).range =
      smallHilbertClassFieldNormSubgroup
        (K := smallHilbertClassFieldBase K)
GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassFieldReciprocityData

Global reciprocity identifies the genuine Galois group of the selected small Hilbert class field with the ordinary ideal class group of the original number field.

Source context 8 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
def smallHilbertClassFieldReciprocityData :
    {e : Gal((smallHilbertClassField K) /
          (smallHilbertClassFieldBase K)) ≃*
        ClassGroup (𝓞 K) //
      ∀ c : IdeleClassGroup (smallHilbertClassFieldBase K),
        e (globalNormResidueMonoidHom
            (smallHilbertClassFieldBase K)
            (smallHilbertClassField K) c) =
          smallHilbertClassGroupCongr
            (smallHilbertClassFieldBaseEquiv (K := K)).symm
            (smallHilbertClassFieldQuotientEquivClassGroup
              (K := smallHilbertClassFieldBase K)
              (QuotientGroup.mk'
                (smallHilbertClassFieldNormSubgroup
                  (K := smallHilbertClassFieldBase K)) c))}
GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassFieldGaloisEquivClassGroup

The reciprocity equivalence from the actual small Hilbert Galois group to the ordinary ideal class group of the original number field.

Source context 8 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
def smallHilbertClassFieldGaloisEquivClassGroup :
    Gal((smallHilbertClassField K) /
        (smallHilbertClassFieldBase K)) ≃*
      ClassGroup (𝓞 K)
GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassFieldGaloisEquivClassGroup_globalNormResidue

Under the small-Hilbert reciprocity equivalence, the actual global norm-residue symbol of an idèle class is its ordinary ideal class, transported back from the concrete base fixed field to the original number field.

Source context 8 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem smallHilbertClassFieldGaloisEquivClassGroup_globalNormResidue
    (c : IdeleClassGroup (smallHilbertClassFieldBase K)) :
    smallHilbertClassFieldGaloisEquivClassGroup (K := K)
        (globalNormResidueMonoidHom
          (smallHilbertClassFieldBase K)
          (smallHilbertClassField K) c) =
      smallHilbertClassGroupCongr
        (smallHilbertClassFieldBaseEquiv (K := K)).symm
        (smallHilbertClassFieldQuotientEquivClassGroup
          (K := smallHilbertClassFieldBase K)
          (QuotientGroup.mk'
            (smallHilbertClassFieldNormSubgroup
              (K := smallHilbertClassFieldBase K)) c))
GlobalClassFieldTheory.GlobalClassFields.smallHilbertClassFieldGaloisEquivClassGroup_idele

Representative form of small-Hilbert reciprocity: the global norm-residue symbol of an actual idèle maps to its ordinary ideal class, with only the canonical base-field transport remaining.

Source context 8 commands

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

open scoped IsMulCommutative NumberField
noncomputable section
namespace GlobalClassFieldTheory
namespace GlobalClassFields
open NumberField
open Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    smallHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem smallHilbertClassFieldGaloisEquivClassGroup_idele
    (a : IdeleGroup (smallHilbertClassFieldBase K)) :
    smallHilbertClassFieldGaloisEquivClassGroup (K := K)
        (globalNormResidueMonoidHom
          (smallHilbertClassFieldBase K)
          (smallHilbertClassField K)
          (QuotientGroup.mk'
            (IdeleGroup.principalSubgroup
              (smallHilbertClassFieldBase K)) a)) =
      smallHilbertClassGroupCongr
        (smallHilbertClassFieldBaseEquiv (K := K)).symm
        (IdeleGroup.idealClass a)