search for:

Synopsis:

sheaf(X,M) -- produce the coherent sheaf on the variety X corresponding to the module M.

If X is the affine variety Spec R, then M should be an R-module. If X is the projective variety Proj R, then M should be a homogeneous R-module.

Code:

     -- ../../../Macaulay2/m2/varieties.m2:101-107
     sheaf(Variety,Module) :=  CoherentSheaf => (X,M) -> if M#?(sheaf,X) then M#(sheaf,X) else M#(sheaf,X) = (
          if ring M =!= ring X then error "expected module and variety to have the same ring";
          if instance(X,ProjectiveVariety) and not isHomogeneous M
          then error "expected a homogeneous module";
          new CoherentSheaf from {
               symbol module => M,
               symbol variety => X

search for: