Module

ContinuousCohomologyRepresentatives.lean

Nyll.GaloisCohomology.Topology.ContinuousCohomologyRepresentatives
2 declarations indexed from sourceView source ↗

Representatives and boundaries in continuous cohomology

The cocycle projection is surjective as a function, and its kernel consists of boundaries. These are statements about the actual topological homology objects, with no exactness assumptions on a coefficient sequence.

Imports2
  • Mathlib.RepresentationTheory.Homological.ContCohomology.Functoriality
  • Mathlib.Algebra.Homology.ShortComplex.ModuleCat
Imported by3

Declarations

ContinuousCohomology.π_surjective

Every continuous cohomology class has a homogeneous cocycle representative.

Source context 5 commands

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

open CategoryTheory CategoryTheory.Limits
namespace ContinuousCohomology
universe u v
variable {R : Type u} [Ring R] [TopologicalSpace R]
variable {G : Type v} [Group G] [TopologicalSpace G] [IsTopologicalGroup G]
theorem π_surjective (A : TopRep.{v} R G) (n : ℕ) :
    Function.Surjective (π A n)
ContinuousCohomology.exists_boundary_of_π_eq_zero

A homogeneous cocycle whose cohomology class is zero is a boundary.

Source context 5 commands

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

open CategoryTheory CategoryTheory.Limits
namespace ContinuousCohomology
universe u v
variable {R : Type u} [Ring R] [TopologicalSpace R]
variable {G : Type v} [Group G] [TopologicalSpace G] [IsTopologicalGroup G]
theorem exists_boundary_of_π_eq_zero (A : TopRep.{v} R G) (n : ℕ)
    (z : cocycles A (n + 1)) (hz : π A (n + 1) z = 0) :
    ∃ c : (TopRep.homogeneousCochains A).X n,
      ((TopRep.homogeneousCochains A).d n (n + 1)).hom c =
        ((TopRep.homogeneousCochains A).iCycles (n + 1)).hom z