Module

Subgroups.lean

Nyll.ProCGroups.GroupTheory.Subgroups
3 declarations indexed from sourceView source ↗

Quotients by kernels

This module realizes the quotient by the kernel of a homomorphism as an injective homomorphism into the target and records its value on quotient representatives.

Imports2
  • Mathlib.GroupTheory.QuotientGroup.Basic
  • Mathlib.Topology.Algebra.OpenSubgroup
Imported by2

Declarations

ProCGroups.GroupTheory.quotientKerEmbedding

The canonical embedding of a kernel quotient into the target range, viewed in the target.

Source context 3 commands

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

namespace ProCGroups.GroupTheory
universe u
variable {G : Type u} [Group G]
def quotientKerEmbedding
    {G T : Type u} [Group G] [Group T] (φ : G →* T) :
    G ⧸ φ.ker →* T
ProCGroups.GroupTheory.quotientKerEmbedding_injective

The quotient-kernel embedding is injective.

Source context 3 commands

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

namespace ProCGroups.GroupTheory
universe u
variable {G : Type u} [Group G]
theorem quotientKerEmbedding_injective
    {G T : Type u} [Group G] [Group T] (φ : G →* T) :
    Function.Injective (quotientKerEmbedding φ)
ProCGroups.GroupTheory.quotientKerEmbedding_mk

The quotient-kernel embedding sends a representative to the corresponding kernel coset.

Source context 3 commands

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

namespace ProCGroups.GroupTheory
universe u
variable {G : Type u} [Group G]
theorem quotientKerEmbedding_mk
    {G T : Type u} [Group G] [Group T] (φ : G →* T) (x : G) :
    quotientKerEmbedding φ (QuotientGroup.mk' φ.ker x) = φ x