Module

CartierEtale.lean

Nyll.SchemeTheory.Divisors.CartierEtale
5 declarations indexed from sourceView source ↗

Effective Cartier divisors under affine flat pullback

The pullback ideal of a locally principal non-zero-divisor remains locally principal and is generated by the image of that non-zero-divisor. Flatness preserves its regularity.

Declarations

AlgebraicGeometry.Scheme.IdealSheafData.IsEffectiveCartier.comap_of_flat_of_isAffineHom

Effective Cartier ideal sheaves remain effective Cartier after affine flat pullback.

Source context 7 commands

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

noncomputable section
open CategoryTheory
namespace AlgebraicGeometry
universe u
namespace Scheme
namespace IdealSheafData
variable {X Y : Scheme.{u}}
theorem IsEffectiveCartier.comap_of_flat_of_isAffineHom
    (I : X.IdealSheafData) (hI : I.IsEffectiveCartier)
    (f : Y ⟶ X) [Flat f] [IsAffineHom f] :
    (I.comap f).IsEffectiveCartier
AlgebraicGeometry.Scheme.EffectiveCartierDivisor.comap

Pullback of an effective Cartier divisor along an affine flat morphism.

Source context 7 commands

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

noncomputable section
open CategoryTheory
namespace AlgebraicGeometry
universe u
namespace Scheme
namespace EffectiveCartierDivisor
variable {X Y : Scheme.{u}}
def comap (D : EffectiveCartierDivisor X)
    (f : Y ⟶ X) [Flat f] [IsAffineHom f] : EffectiveCartierDivisor Y
AlgebraicGeometry.Scheme.EffectiveCartierDivisor.coe_comap
Source context 7 commands

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

noncomputable section
open CategoryTheory
namespace AlgebraicGeometry
universe u
namespace Scheme
namespace EffectiveCartierDivisor
variable {X Y : Scheme.{u}}
lemma coe_comap (D : EffectiveCartierDivisor X)
    (f : Y ⟶ X) [Flat f] [IsAffineHom f] :
    (D.comap f : Y.IdealSheafData) = D.1.comap f
AlgebraicGeometry.Scheme.EffectiveCartierDivisor.comapFiniteEtale

Pullback along a finite-etale object, with all morphism-property instances supplied by the object itself.

Source context 7 commands

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

noncomputable section
open CategoryTheory
namespace AlgebraicGeometry
universe u
namespace Scheme
namespace EffectiveCartierDivisor
variable {X Y : Scheme.{u}}
def comapFiniteEtale (D : EffectiveCartierDivisor X)
    (Y' : FiniteEtale X) : EffectiveCartierDivisor Y'.left
AlgebraicGeometry.Scheme.EffectiveCartierDivisor.coe_comapFiniteEtale
Source context 7 commands

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

noncomputable section
open CategoryTheory
namespace AlgebraicGeometry
universe u
namespace Scheme
namespace EffectiveCartierDivisor
variable {X Y : Scheme.{u}}
lemma coe_comapFiniteEtale (D : EffectiveCartierDivisor X)
    (Y' : FiniteEtale X) :
    (D.comapFiniteEtale Y' : Y'.left.IdealSheafData) = D.1.comap Y'.hom