Module

BigActual.lean

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

Big Hilbert reciprocity over the realized base field

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

Declarations

GlobalClassFieldTheory.GlobalClassFields.bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
Source context 6 commands

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

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

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

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 Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem bigHilbertClassField_ideleClassNorm_range_eq_intrinsic :
    (_root_.ideleClassNorm
      (bigHilbertClassFieldBase K)
      (bigHilbertClassField K)).range =
      bigHilbertClassFieldNormSubgroup
        (K := bigHilbertClassFieldBase K)
GlobalClassFieldTheory.GlobalClassFields.bigHilbertClassFieldReciprocityData

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

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 Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
def bigHilbertClassFieldReciprocityData :
    {e : Gal((bigHilbertClassField K) /
          (bigHilbertClassFieldBase K)) ≃*
        RayClass.NarrowClassGroup K //
      ∀ c : IdeleClassGroup (bigHilbertClassFieldBase K),
        e (globalNormResidueMonoidHom
            (bigHilbertClassFieldBase K)
            (bigHilbertClassField K) c) =
          bigHilbertNarrowClassGroupCongr
            (bigHilbertClassFieldBaseEquiv (K := K)).symm
            (bigHilbertClassFieldQuotientEquivNarrowClassGroup
              (K := bigHilbertClassFieldBase K)
              (QuotientGroup.mk'
                (bigHilbertClassFieldNormSubgroup
                  (K := bigHilbertClassFieldBase K)) c))}
GlobalClassFieldTheory.GlobalClassFields.bigHilbertClassFieldGaloisEquivNarrowClassGroup

The reciprocity equivalence from the actual big Hilbert Galois group to the narrow class group of the original number field.

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 Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
def bigHilbertClassFieldGaloisEquivNarrowClassGroup :
    Gal((bigHilbertClassField K) /
        (bigHilbertClassFieldBase K)) ≃*
      RayClass.NarrowClassGroup K
GlobalClassFieldTheory.GlobalClassFields.bigHilbertClassFieldGaloisEquivNarrowClassGroup_globalNormResidue

Under big-Hilbert reciprocity, the actual global norm-residue symbol is the narrow ideal class of its idèle-class representative, transported back to the original number field.

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 Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem bigHilbertClassFieldGaloisEquivNarrowClassGroup_globalNormResidue
    (c : IdeleClassGroup (bigHilbertClassFieldBase K)) :
    bigHilbertClassFieldGaloisEquivNarrowClassGroup (K := K)
        (globalNormResidueMonoidHom
          (bigHilbertClassFieldBase K)
          (bigHilbertClassField K) c) =
      bigHilbertNarrowClassGroupCongr
        (bigHilbertClassFieldBaseEquiv (K := K)).symm
        (bigHilbertClassFieldQuotientEquivNarrowClassGroup
          (K := bigHilbertClassFieldBase K)
          (QuotientGroup.mk'
            (bigHilbertClassFieldNormSubgroup
              (K := bigHilbertClassFieldBase K)) c))
GlobalClassFieldTheory.GlobalClassFields.bigHilbertClassFieldGaloisEquivNarrowClassGroup_idele

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

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 Reciprocity
variable {K : Type} [Field K] [NumberField K]
local instance
    bigHilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
    {F : Type} [Field F] [NumberField F] :
    IsMulCommutative (IdeleClassGroup F) :=
  hilbertClassFieldReciprocityIdeleClassGroupIsMulCommutative
theorem bigHilbertClassFieldGaloisEquivNarrowClassGroup_idele
    (a : IdeleGroup (bigHilbertClassFieldBase K)) :
    bigHilbertClassFieldGaloisEquivNarrowClassGroup (K := K)
        (globalNormResidueMonoidHom
          (bigHilbertClassFieldBase K)
          (bigHilbertClassField K)
          (QuotientGroup.mk'
            (IdeleGroup.principalSubgroup
              (bigHilbertClassFieldBase K)) a)) =
      bigHilbertNarrowClassGroupCongr
        (bigHilbertClassFieldBaseEquiv (K := K)).symm
        (QuotientGroup.mk'
          (RayClass.narrowDenominator
            (K := bigHilbertClassFieldBase K)) a)