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Structure Sheaf on Basic Opens #728

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merged 34 commits into from
Mar 9, 2022
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@mzeuner mzeuner commented Feb 24, 2022

This PR contains a proof that the structure presheaf defined on the basic opens of the Zariski lattice is indeed a sheaf.

@mzeuner mzeuner changed the title Pb square in comm algs Structure Sheaf on Basic Opens Feb 24, 2022
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Discussion with @mortberg

R[1/fg]≡R[1/f][1/g] : R[1/fg]AsCommAlgebra ≡ R[1/f][1/g]AsCommAlgebra
R[1/fg]≡R[1/f][1/g] = uaCommAlgebra (R[1/fg]AlgCharEquiv _ _ pathtoR[1/fg])

doubleLocCancel : g ∈ᵢ √ ⟨ replicateFinVec 1 f ⟩ → R[1/f][1/g]AsCommAlgebra ≡ R[1/g]AsCommAlgebra
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Nicer notation for ⟨ replicateFinVec 1 f ⟩ , maybe some notation for singleton vector?

open IsBasis hB

private
BasisCat = MeetSemilatticeCategory (Basis→MeetSemilattice L L' hB)
DLCat = DistLatticeCategory L
BasisCat = ΣPropCat DLCat L' -- MeetSemilatticeCategory (Basis→MeetSemilattice L L' hB)
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delete comment

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done

-- we get a pullback square in comm rings that then gives us the desired
-- square in R-algebras that we want to transport
theRingCospan = fgCospan R[1/ h ]AsCommRing (f /1) (g /1)
theRingPullback = fgPullback R[1/ h ]AsCommRing (f /1) (g /1) 1∈fgIdeal
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draw the square

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done

@mzeuner
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mzeuner commented Mar 1, 2022

One thing that we should also consider is splitting up the file Algebra.ZariskiLattice.Base
I think the Base file should only contain the construction of the lattice and the proof that it's small.
Then there should be a file for the proof of the universal property and then one for the basic opens.
The latter would contain the proof that the basic opens do indeed form a basis plus the construction
of the structure sheaf and verification of the sheaf property.

Hopefully that would also speed up type-checking. What do you think @mortberg ?

@mortberg mortberg merged commit 420b0db into agda:master Mar 9, 2022
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2 participants