Module

Subcanonical.lean

Nyll.EtaleCohomology.Sites.Subcanonical
2 declarations indexed from sourceView source ↗

Subcanonicity of the étale sites

The big étale topology is coarser than the subcanonical fppf topology. The inclusion of the small étale site into the slice of the big site is fully faithful, preserves finite limits, and preserves covering sieves. Consequently its representable presheaves are sheaves as well.

Imports9
  • Mathlib.AlgebraicGeometry.Sites.Etale
  • Mathlib.AlgebraicGeometry.Sites.Fpqc
  • Mathlib.AlgebraicGeometry.Sites.Pretopology
  • Mathlib.CategoryTheory.Sites.Subcanonical
  • Mathlib.CategoryTheory.Sites.SubcanonicalOver
  • Mathlib.CategoryTheory.Sites.DenseSubsite.InducedTopology
  • Mathlib.CategoryTheory.Sites.CoverPreserving
  • Mathlib.CategoryTheory.Functor.Flat
  • Mathlib.CategoryTheory.Limits.MorphismProperty
Imported by9

Declarations

EtaleCohomology.etaleTopology_subcanonical

Representable presheaves on the big étale site are sheaves, by fppf descent.

Source context 3 commands

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

open AlgebraicGeometry CategoryTheory
universe u
namespace EtaleCohomology
instance etaleTopology_subcanonical : Scheme.etaleTopology.{u}.Subcanonical
EtaleCohomology.smallEtaleTopology_subcanonical

Representable presheaves on the small étale site are sheaves.

Source context 3 commands

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

open AlgebraicGeometry CategoryTheory
universe u
namespace EtaleCohomology
instance smallEtaleTopology_subcanonical (X : Scheme.{u}) :
    X.smallEtaleTopology.Subcanonical