Module

GenericFieldSource.lean

Nyll.EtaleFundamentalGroups.Normalization.GenericFieldSource
4 declarations indexed from sourceView source ↗

Field sources of dominant preimmersions

A dominant preimmersion from the spectrum of a field into an integral scheme is its generic-point morphism, up to the actual isomorphism of source schemes induced by the map on the generic stalk.

Declarations

EtaleFundamentalGroups.dominant_field_closedPoint_eq_genericPoint

A dominant morphism from a field spectrum sends its unique point to the generic point.

Source context 5 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry TopologicalSpace
namespace EtaleFundamentalGroups
universe u
variable {Y : Scheme.{u}} [IsIntegral Y] {L : Type u} [Field L]
  (p : Spec (.of L) ⟶ Y) [IsDominant p]
theorem dominant_field_closedPoint_eq_genericPoint :
    p (IsLocalRing.closedPoint (CommRingCat.of L)) = genericPoint Y
EtaleFundamentalGroups.genericFieldSourceRingEquiv

The generic-stalk map of a dominant preimmersion from Spec L is a field isomorphism. Surjectivity comes from the preimmersion hypothesis.

Source context 6 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry TopologicalSpace
namespace EtaleFundamentalGroups
universe u
variable {Y : Scheme.{u}} [IsIntegral Y] {L : Type u} [Field L]
  (p : Spec (.of L) ⟶ Y) [IsDominant p]
variable [IsPreimmersion p]
def genericFieldSourceRingEquiv : Y.functionField ≃+* L
EtaleFundamentalGroups.genericFieldSourceIso

A field spectrum mapping dominantly by a preimmersion is isomorphic to the spectrum of the target's function field.

Source context 6 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry TopologicalSpace
namespace EtaleFundamentalGroups
universe u
variable {Y : Scheme.{u}} [IsIntegral Y] {L : Type u} [Field L]
  (p : Spec (.of L) ⟶ Y) [IsDominant p]
variable [IsPreimmersion p]
def genericFieldSourceIso : Spec (.of L) ≅ Spec Y.functionField
EtaleFundamentalGroups.genericFieldSourceIso_hom_fromSpecStalk

The source isomorphism identifies the original morphism with the canonical generic-point morphism.

Source context 6 commands

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

noncomputable section
open CategoryTheory AlgebraicGeometry TopologicalSpace
namespace EtaleFundamentalGroups
universe u
variable {Y : Scheme.{u}} [IsIntegral Y] {L : Type u} [Field L]
  (p : Spec (.of L) ⟶ Y) [IsDominant p]
variable [IsPreimmersion p]
theorem genericFieldSourceIso_hom_fromSpecStalk :
    (genericFieldSourceIso p).hom ≫ Y.fromSpecStalk (genericPoint Y) = p