Open immersions of structured spaces #
We say that a morphism of presheafed spaces f : X ⟶ Y
is an open immersion if
the underlying map of spaces is an open embedding f : X ⟶ U ⊆ Y
,
and the sheaf map Y(V) ⟶ f _* X(V)
is an iso for each V ⊆ U
.
Abbreviations are also provided for SheafedSpace
, LocallyRingedSpace
and Scheme
.
Main definitions #
AlgebraicGeometry.PresheafedSpace.IsOpenImmersion
: theProp
-valued typeclass asserting that a PresheafedSpace homf
is an open_immersion.AlgebraicGeometry.IsOpenImmersion
: theProp
-valued typeclass asserting that a Scheme morphismf
is an open_immersion.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.isoRestrict
: The source of an open immersion is isomorphic to the restriction of the target onto the image.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.lift
: Any morphism whose range is contained in an open immersion factors though the open immersion.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toSheafedSpace
: Iff : X ⟶ Y
is an open immersion of presheafed spaces, andY
is a sheafed space, thenX
is also a sheafed space. The morphism as morphisms of sheafed spaces is given bytoSheafedSpaceHom
.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toLocallyRingedSpace
: Iff : X ⟶ Y
is an open immersion of presheafed spaces, andY
is a locally ringed space, thenX
is also a locally ringed space. The morphism as morphisms of locally ringed spaces is given bytoLocallyRingedSpaceHom
.
Main results #
AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.comp
: The composition of two open immersions is an open immersion.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.ofIso
: An iso is an open immersion.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.to_iso
: A surjective open immersion is an isomorphism.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.stalk_iso
: An open immersion induces an isomorphism on stalks.AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.hasPullback_of_left
: Iff
is an open immersion, then the pullback(f, g)
exists (and the forgetful functor toTopCat
preserves it).AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.pullbackSndOfLeft
: Open immersions are stable under pullbacks.AlgebraicGeometry.SheafedSpace.IsOpenImmersion.of_stalk_iso
An (topological) open embedding between two sheafed spaces is an open immersion if all the stalk maps are isomorphisms.
An open immersion of PresheafedSpaces is an open embedding f : X ⟶ U ⊆ Y
of the underlying
spaces, such that the sheaf map Y(V) ⟶ f _* X(V)
is an iso for each V ⊆ U
.
- base_open : IsOpenEmbedding ⇑f.base
the underlying continuous map of underlying spaces from the source to an open subset of the target.
- c_iso : ∀ (U : TopologicalSpace.Opens ↑↑X), CategoryTheory.IsIso (f.c.app (Opposite.op (⋯.functor.obj U)))
the underlying sheaf morphism is an isomorphism on each open subset
Instances
the underlying continuous map of underlying spaces from the source to an open subset of the target.
the underlying sheaf morphism is an isomorphism on each open subset
A morphism of SheafedSpaces is an open immersion if it is an open immersion as a morphism of PresheafedSpaces
Equations
Instances For
A morphism of LocallyRingedSpaces is an open immersion if it is an open immersion as a morphism of SheafedSpaces
Equations
Instances For
The functor Opens X ⥤ Opens Y
associated with an open immersion f : X ⟶ Y
.
Equations
Instances For
An open immersion f : X ⟶ Y
induces an isomorphism X ≅ Y|_{f(X)}
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
The composition of two open immersions is an open immersion.
Equations
- ⋯ = ⋯
For an open immersion f : X ⟶ Y
and an open set U ⊆ X
, we have the map X(U) ⟶ Y(U)
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
A variant of app_inv_app
that gives an eqToHom
instead of homOfLe
.
An isomorphism is an open immersion.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
An open immersion is an iso if the underlying continuous map is epi.
Equations
- ⋯ = ⋯
(Implementation.) The projection map when constructing the pullback along an open immersion.
Equations
- One or more equations did not get rendered due to their size.
Instances For
We construct the pullback along an open immersion via restricting along the pullback of the maps of underlying spaces (which is also an open embedding).
Equations
- One or more equations did not get rendered due to their size.
Instances For
(Implementation.) Any cone over cospan f g
indeed factors through the constructed cone.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
The constructed pullback cone is indeed the pullback.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Open immersions are stable under base-change.
Equations
- ⋯ = ⋯
Open immersions are stable under base-change.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- One or more equations did not get rendered due to their size.
The universal property of open immersions:
For an open immersion f : X ⟶ Z
, given any morphism of schemes g : Y ⟶ Z
whose topological
image is contained in the image of f
, we can lift this morphism to a unique Y ⟶ X
that
commutes with these maps.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Two open immersions with equal range is isomorphic.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If X ⟶ Y
is an open immersion, and Y
is a SheafedSpace, then so is X
.
Equations
- AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toSheafedSpace Y f = { toPresheafedSpace := X, IsSheaf := ⋯ }
Instances For
If X ⟶ Y
is an open immersion of PresheafedSpaces, and Y
is a SheafedSpace, we can
upgrade it into a morphism of SheafedSpaces.
Instances For
Equations
- ⋯ = H
If X ⟶ Y
is an open immersion, and Y
is a LocallyRingedSpace, then so is X
.
Equations
- One or more equations did not get rendered due to their size.
Instances For
If X ⟶ Y
is an open immersion of PresheafedSpaces, and Y
is a LocallyRingedSpace, we can
upgrade it into a morphism of LocallyRingedSpace.
Equations
- AlgebraicGeometry.PresheafedSpace.IsOpenImmersion.toLocallyRingedSpaceHom Y f = { toHom := f, prop := ⋯ }
Instances For
Equations
- ⋯ = H
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Open immersions are stable under base-change.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Suppose X Y : SheafedSpace C
, where C
is a concrete category,
whose forgetful functor reflects isomorphisms, preserves limits and filtered colimits.
Then a morphism X ⟶ Y
that is a topological open embedding
is an open immersion iff every stalk map is an iso.
The functor Opens X ⥤ Opens Y
associated with an open immersion f : X ⟶ Y
.
Equations
Instances For
An open immersion f : X ⟶ Y
induces an isomorphism X ≅ Y|_{f(X)}
.
Equations
Instances For
For an open immersion f : X ⟶ Y
and an open set U ⊆ X
, we have the map X(U) ⟶ Y(U)
.
Equations
Instances For
Equations
- ⋯ = ⋯
A variant of app_inv_app
that gives an eqToHom
instead of homOfLe
.
Equations
- ⋯ = ⋯
An open immersion is an iso if the underlying continuous map is epi.
Equations
- ⋯ = ⋯
Alias of AlgebraicGeometry.SheafedSpace.IsOpenImmersion.sigma_ι_isOpenEmbedding
.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = H
An explicit pullback cone over cospan f g
if f
is an open immersion.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
The constructed pullbackConeOfLeft
is indeed limiting.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Open immersions are stable under base-change.
Equations
- ⋯ = ⋯
Open immersions are stable under base-change.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- ⋯ = H
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
Equations
- One or more equations did not get rendered due to their size.
The universal property of open immersions:
For an open immersion f : X ⟶ Z
, given any morphism of schemes g : Y ⟶ Z
whose topological
image is contained in the image of f
, we can lift this morphism to a unique Y ⟶ X
that
commutes with these maps.
Equations
- One or more equations did not get rendered due to their size.
Instances For
An open immersion is isomorphic to the induced open subscheme on its image.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The functor Opens X ⥤ Opens Y
associated with an open immersion f : X ⟶ Y
.
Equations
Instances For
Suppose X Y : SheafedSpace C
, where C
is a concrete category,
whose forgetful functor reflects isomorphisms, preserves limits and filtered colimits.
Then a morphism X ⟶ Y
that is a topological open embedding
is an open immersion iff every stalk map is an iso.
For an open immersion f : X ⟶ Y
and an open set U ⊆ X
, we have the map X(U) ⟶ Y(U)
.
Equations
Instances For
Equations
- ⋯ = ⋯
A variant of app_inv_app
that gives an eqToHom
instead of homOfLe
.
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯