PresheafedSpace C
has colimits. #
If C
has limits, then the category PresheafedSpace C
has colimits,
and the forgetful functor to TopCat
preserves these colimits.
When restricted to a diagram where the underlying continuous maps are open embeddings, this says that we can glue presheaved spaces.
Given a diagram F : J ⥤ PresheafedSpace C
,
we first build the colimit of the underlying topological spaces,
as colimit (F ⋙ PresheafedSpace.forget C)
. Call that colimit space X
.
Our strategy is to push each of the presheaves F.obj j
forward along the continuous map colimit.ι (F ⋙ PresheafedSpace.forget C) j
to X
.
Since pushforward is functorial, we obtain a diagram J ⥤ (presheaf C X)ᵒᵖ
of presheaves on a single space X
.
(Note that the arrows now point the other direction,
because this is the way PresheafedSpace C
is set up.)
The limit of this diagram then constitutes the colimit presheaf.
Given a diagram of PresheafedSpace C
s, its colimit is computed by pushing the sheaves onto
the colimit of the underlying spaces, and taking componentwise limit.
This is the componentwise diagram for an open set U
of the colimit of the underlying spaces.
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Given a diagram of presheafed spaces,
we can push all the presheaves forward to the colimit X
of the underlying topological spaces,
obtaining a diagram in (Presheaf C X)ᵒᵖ
.
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Auxiliary definition for AlgebraicGeometry.PresheafedSpace.instHasColimits
.
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Auxiliary definition for AlgebraicGeometry.PresheafedSpace.instHasColimits
.
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Auxiliary definition for AlgebraicGeometry.PresheafedSpace.colimitCoconeIsColimit
.
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Auxiliary definition for AlgebraicGeometry.PresheafedSpace.colimitCoconeIsColimit
.
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Auxiliary definition for AlgebraicGeometry.PresheafedSpace.instHasColimits
.
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- AlgebraicGeometry.PresheafedSpace.instPreservesColimitsOfShapePresheafedSpaceCategoryOfPresheafedSpacesTopCatInstTopCatLargeCategoryForget = CategoryTheory.Limits.PreservesColimitsOfShape.mk
When C
has limits, the category of presheaved spaces with values in C
itself has colimits.
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The underlying topological space of a colimit of presheaved spaces is the colimit of the underlying topological spaces.
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- AlgebraicGeometry.PresheafedSpace.forgetPreservesColimits = CategoryTheory.Limits.PreservesColimitsOfSize.mk
The components of the colimit of a diagram of PresheafedSpace C
is obtained
via taking componentwise limits.
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