Module

Etale.lean

Nyll.EtaleCohomology.Classical.Etale
4 declarations indexed from sourceView source ↗

Classical étale cohomology with module coefficients

All site and Ext hypotheses are supplied by the existing affine étale comparison and Grothendieck abelian category instances. The underlying groups are Sheaf.H on the small étale site.

Imports8
Imported by4

Declarations

EtaleCohomology.etaleCohomology

Classical étale cohomology, bundled with its coefficient module.

Source context 5 commands

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

noncomputable section
universe u
open AlgebraicGeometry CategoryTheory CategoryTheory.Limits Opposite
namespace EtaleCohomology
variable (X : Scheme.{u}) (R : Type u) [CommRing R]
def etaleCohomology (F : Sheaf X.smallEtaleTopology (ModuleCat.{u} R)) (n : ℕ) :
    ModuleCat.{u} R
EtaleCohomology.etaleCohomologyZeroEquiv

Degree-zero étale cohomology is the module of sections over the terminal étale object.

Source context 5 commands

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

noncomputable section
universe u
open AlgebraicGeometry CategoryTheory CategoryTheory.Limits Opposite
namespace EtaleCohomology
variable (X : Scheme.{u}) (R : Type u) [CommRing R]
def etaleCohomologyZeroEquiv (F : Sheaf X.smallEtaleTopology (ModuleCat.{u} R)) :
    etaleCohomology X R F 0 ≃ₗ[R]
      F.obj.obj (op (⊤_ X.Etale))
EtaleCohomology.finiteCoefficientSheaf

The finite-level coefficient object on the actual small étale site.

Source context 5 commands

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

noncomputable section
universe u
open AlgebraicGeometry CategoryTheory CategoryTheory.Limits Opposite
namespace EtaleCohomology
variable (X : Scheme.{u}) (R : Type u) [CommRing R]
def finiteCoefficientSheaf (ℓ n : ℕ) :
    Sheaf X.smallEtaleTopology (ModuleCat.{u} (ZMod (ℓ ^ (n + 1))))
EtaleCohomology.finiteCoefficientCohomologyZeroEquiv

Finite-level classical cohomology and global sections agree in degree zero.

Source context 5 commands

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

noncomputable section
universe u
open AlgebraicGeometry CategoryTheory CategoryTheory.Limits Opposite
namespace EtaleCohomology
variable (X : Scheme.{u}) (R : Type u) [CommRing R]
def finiteCoefficientCohomologyZeroEquiv (ℓ n : ℕ) :
    Classical.cohomology.{u + 1, u, u, 0, u}
      (finiteCoefficientSheaf X ℓ n) 0 ≃ₗ[ZMod (ℓ ^ (n + 1))]
      (finiteCoefficientSheaf X ℓ n).obj.obj
        (op (⊤_ X.Etale))