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changes to demo
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mkbrown5 committed Jun 5, 2024
1 parent bfd97db commit a012641
Showing 1 changed file with 6 additions and 9 deletions.
15 changes: 6 additions & 9 deletions DbCY/DbCY.m2
Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,7 @@ singularityToDerived(Matrix, ZZ, ZZ) := (f, i, j) -> (
if depth(target f) < d or depth(source f) < d then error "Not a map of MCM modules.";
g := resolution(orlovTruncateGeqDualize(f, i), LengthLimit => j);
gdual := dual g;
orlovTruncateLess(gdual, i)
sheaf orlovTruncateLess(gdual, i)
)

end;
Expand Down Expand Up @@ -220,16 +220,13 @@ f = sum for i from 0 to 4 list x_i^5
R = S / ideal(f) --affine cone of the quintic
kk = coker vars R --the residue field of R
F = singularityToDerived(kk, 0, 7)
--This computes \Phi(kk) (up to sheafification).
--We will eventually interface with "Varieties" package to implement the associated complex of sheaves.
--The complex \Phi(kk) has infinite length; it is unbounded on the right. We take a length 7 approximation here.
--This is \Phi(kk) before sheafifying. The complex has infinite length; it is unbounded on the right.
--The tail is a matrix factorization.

X = Proj(R)
Ftilde = sheaf F
--This is \Phi(kk).
--What is the homology of this complex?
homologies = for i from 0 to 3 list prune HH_i F
--Let's sheafify these:
sheaf HH_0 F == 0
sheaf prune HH_3 F
prune HH Ftilde
--Thus, \Phi(kk) = O_X[-3].

--Future work: implement the functor going the opposite direction.
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