Module

TateTransport.lean

Nyll.ClassFieldTheory.LocalClassFieldTheory.Finite.LocalReciprocity.TateTransport
10 declarations indexed from sourceView source ↗

The local class-field-axiom theorem: transport of cyclic Tate complexes

The fixed-field realization of an abstract extension changes both the presentation of its cyclic group and the presentation of its coefficient module. This file records the two honest functorial comparisons needed to transport the local class-field-axiom theorem: reindexing a representation along a group isomorphism and replacing a representation by an isomorphic one.

Declarations

LocalClassFieldTheory.map_cyclicGenerator

A generator remains a generator after applying a group isomorphism.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section CyclicGenerator
variable {Q P : Type} [Group Q] [Group P]
theorem map_cyclicGenerator (e : Q ≃* P) (g : Q)
    (hg : ∀ q : Q, q ∈ Subgroup.zpowers g) :
    ∀ p : P, p ∈ Subgroup.zpowers (e g)
LocalClassFieldTheory.res_norm_eq
Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section GroupEquiv
variable {R Q P : Type} [CommRing R]
  [CommGroup Q] [CommGroup P] [Fintype Q] [Fintype P]
theorem res_norm_eq (e : Q ≃* P) (A : Rep R P) :
    let Ares : Rep R Q :=
      Rep.res e.toMonoidHom A
    ModuleCat.ofHom Ares.norm.hom.toLinearMap =
      ModuleCat.ofHom A.norm.hom.toLinearMap := by
  let Ares : Rep R Q :=
    Rep.res e.toMonoidHom A
  apply congrArg ModuleCat.ofHom
  change Representation.norm Ares.ρ = Representation.norm A.ρ
  simp only [Representation.norm]
  exact Fintype.sum_equiv e.toEquiv
    (fun q : Q => Ares.ρ q)
    (fun p : P => A.ρ p) (fun _ => rfl)
LocalClassFieldTheory.normHomCompSubResEquivIso

Reindexing along a group isomorphism preserves the cyclic H⁰ short complex.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section GroupEquiv
variable {R Q P : Type} [CommRing R]
  [CommGroup Q] [CommGroup P] [Fintype Q] [Fintype P]
def normHomCompSubResEquivIso
    (e : Q ≃* P) (A : Rep R P) (g : Q) :
    Rep.FiniteCyclicGroup.normHomCompSub
        (Rep.res e.toMonoidHom A) g ≅
      Rep.FiniteCyclicGroup.normHomCompSub A (e g)
LocalClassFieldTheory.subCompNormHomResEquivIso

Reindexing along a group isomorphism preserves the cyclic H⁻¹ short complex.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section GroupEquiv
variable {R Q P : Type} [CommRing R]
  [CommGroup Q] [CommGroup P] [Fintype Q] [Fintype P]
def subCompNormHomResEquivIso
    (e : Q ≃* P) (A : Rep R P) (g : Q) :
    Rep.FiniteCyclicGroup.subCompNormHom
        (Rep.res e.toMonoidHom A) g ≅
      Rep.FiniteCyclicGroup.subCompNormHom A (e g)
LocalClassFieldTheory.normHomCompSubHomologyResEquivIso

Homology-level group-reindexing comparison in degree zero.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section GroupEquiv
variable {R Q P : Type} [CommRing R]
  [CommGroup Q] [CommGroup P] [Fintype Q] [Fintype P]
def normHomCompSubHomologyResEquivIso
    (e : Q ≃* P) (A : Rep R P) (g : Q) :
    (Rep.FiniteCyclicGroup.normHomCompSub
        (Rep.res e.toMonoidHom A) g).homology ≅
      (Rep.FiniteCyclicGroup.normHomCompSub A (e g)).homology
LocalClassFieldTheory.subCompNormHomHomologyResEquivIso

Homology-level group-reindexing comparison in degree minus one.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section GroupEquiv
variable {R Q P : Type} [CommRing R]
  [CommGroup Q] [CommGroup P] [Fintype Q] [Fintype P]
def subCompNormHomHomologyResEquivIso
    (e : Q ≃* P) (A : Rep R P) (g : Q) :
    (Rep.FiniteCyclicGroup.subCompNormHom
        (Rep.res e.toMonoidHom A) g).homology ≅
      (Rep.FiniteCyclicGroup.subCompNormHom A (e g)).homology
LocalClassFieldTheory.normHomCompSubIsoOfRepIso

Isomorphic representations have isomorphic cyclic H⁰ short complexes.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section RepresentationIso
variable {R Q : Type} [CommRing R] [CommGroup Q] [Fintype Q]
def normHomCompSubIsoOfRepIso
    {M N : Rep R Q} (e : M ≅ N) (g : Q) :
    Rep.FiniteCyclicGroup.normHomCompSub M g ≅
      Rep.FiniteCyclicGroup.normHomCompSub N g
LocalClassFieldTheory.subCompNormHomIsoOfRepIso

Isomorphic representations have isomorphic cyclic H⁻¹ short complexes.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section RepresentationIso
variable {R Q : Type} [CommRing R] [CommGroup Q] [Fintype Q]
def subCompNormHomIsoOfRepIso
    {M N : Rep R Q} (e : M ≅ N) (g : Q) :
    Rep.FiniteCyclicGroup.subCompNormHom M g ≅
      Rep.FiniteCyclicGroup.subCompNormHom N g
LocalClassFieldTheory.normHomCompSubHomologyIsoOfRepIso

Homology-level representation-isomorphism comparison in degree zero.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section RepresentationIso
variable {R Q : Type} [CommRing R] [CommGroup Q] [Fintype Q]
def normHomCompSubHomologyIsoOfRepIso
    {M N : Rep R Q} (e : M ≅ N) (g : Q) :
    (Rep.FiniteCyclicGroup.normHomCompSub M g).homology ≅
      (Rep.FiniteCyclicGroup.normHomCompSub N g).homology
LocalClassFieldTheory.subCompNormHomHomologyIsoOfRepIso

Homology-level representation-isomorphism comparison in degree minus one.

Source context 6 commands

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

namespace LocalClassFieldTheory
open ClassFormation
noncomputable section
open CategoryTheory
section RepresentationIso
variable {R Q : Type} [CommRing R] [CommGroup Q] [Fintype Q]
def subCompNormHomHomologyIsoOfRepIso
    {M N : Rep R Q} (e : M ≅ N) (g : Q) :
    (Rep.FiniteCyclicGroup.subCompNormHom M g).homology ≅
      (Rep.FiniteCyclicGroup.subCompNormHom N g).homology