The category of locally ringed spaces #
We define (bundled) locally ringed spaces (as SheafedSpace CommRing
along with the fact that the
stalks are local rings), and morphisms between these (morphisms in SheafedSpace
with
is_local_ring_hom
on the stalk maps).
A LocallyRingedSpace
is a topological space equipped with a sheaf of commutative rings
such that all the stalks are local rings.
A morphism of locally ringed spaces is a morphism of ringed spaces such that the morphisms induced on stalks are local ring homomorphisms.
- carrier : TopCat
- presheaf : TopCat.Presheaf CommRingCat ↑self.toPresheafedSpace
- IsSheaf : TopCat.Presheaf.IsSheaf self.presheaf
- localRing : ∀ (x : ↑↑self.toPresheafedSpace), LocalRing ↑(TopCat.Presheaf.stalk self.presheaf x)
Stalks of a locally ringed space are local rings.
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An alias for to_SheafedSpace
, where the result type is a RingedSpace
.
This allows us to use dot-notation for the RingedSpace
namespace.
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- AlgebraicGeometry.LocallyRingedSpace.toRingedSpace X = X.toSheafedSpace
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The underlying topological space of a locally ringed space.
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- AlgebraicGeometry.LocallyRingedSpace.toTopCat X = ↑X.toPresheafedSpace
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- (_ : LocalRing ↑(AlgebraicGeometry.PresheafedSpace.stalk X.toPresheafedSpace x)) = (_ : LocalRing ↑(TopCat.Presheaf.stalk X.presheaf x))
The structure sheaf of a locally ringed space.
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- AlgebraicGeometry.LocallyRingedSpace.𝒪 X = AlgebraicGeometry.SheafedSpace.sheaf X.toSheafedSpace
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A morphism of locally ringed spaces is a morphism of ringed spaces such that the morphisms induced on stalks are local ring homomorphisms.
- val : X.toSheafedSpace ⟶ Y.toSheafedSpace
the underlying morphism between ringed spaces
- prop : ∀ (x : ↑↑X.toPresheafedSpace), IsLocalRingHom (AlgebraicGeometry.PresheafedSpace.stalkMap self.val x)
the underlying morphism induces a local ring homomorphism on stalks
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The stalk of a locally ringed space, just as a CommRing
.
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- AlgebraicGeometry.LocallyRingedSpace.stalk X x = TopCat.Presheaf.stalk X.presheaf x
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- (_ : LocalRing ↑(AlgebraicGeometry.LocallyRingedSpace.stalk X x)) = (_ : LocalRing ↑(TopCat.Presheaf.stalk X.presheaf x))
A morphism of locally ringed spaces f : X ⟶ Y
induces
a local ring homomorphism from Y.stalk (f x)
to X.stalk x
for any x : X
.
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- (_ : IsLocalRingHom (AlgebraicGeometry.LocallyRingedSpace.stalkMap f x)) = (_ : IsLocalRingHom (AlgebraicGeometry.PresheafedSpace.stalkMap f.val x))
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- (_ : IsLocalRingHom (AlgebraicGeometry.PresheafedSpace.stalkMap f.val x)) = (_ : IsLocalRingHom (AlgebraicGeometry.PresheafedSpace.stalkMap f.val x))
The identity morphism on a locally ringed space.
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Composition of morphisms of locally ringed spaces.
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The category of locally ringed spaces.
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- AlgebraicGeometry.LocallyRingedSpace.instCategoryLocallyRingedSpace = CategoryTheory.Category.mk
The forgetful functor from LocallyRingedSpace
to SheafedSpace CommRing
.
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The forgetful functor from LocallyRingedSpace
to Top
.
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Given two locally ringed spaces X
and Y
, an isomorphism between X
and Y
as sheafed
spaces can be lifted to a morphism X ⟶ Y
as locally ringed spaces.
See also iso_of_SheafedSpace_iso
.
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Given two locally ringed spaces X
and Y
, an isomorphism between X
and Y
as sheafed
spaces can be lifted to an isomorphism X ⟶ Y
as locally ringed spaces.
This is related to the property that the functor forget_to_SheafedSpace
reflects isomorphisms.
In fact, it is slightly stronger as we do not require f
to come from a morphism between
locally ringed spaces.
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- (_ : CategoryTheory.IsIso f.val) = (_ : CategoryTheory.IsIso (AlgebraicGeometry.LocallyRingedSpace.forgetToSheafedSpace.toPrefunctor.map f))
The restriction of a locally ringed space along an open embedding.
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The canonical map from the restriction to the subspace.
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The restriction of a locally ringed space X
to the top subspace is isomorphic to X
itself.
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The global sections, notated Gamma.
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- AlgebraicGeometry.LocallyRingedSpace.Γ = CategoryTheory.Functor.comp AlgebraicGeometry.LocallyRingedSpace.forgetToSheafedSpace.op AlgebraicGeometry.SheafedSpace.Γ
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- (_ : Nontrivial ↑(X.presheaf.toPrefunctor.obj (Opposite.op U))) = (_ : Nontrivial ↑(X.presheaf.toPrefunctor.obj (Opposite.op U)))