Opened 9 years ago
Last modified 4 years ago
#11394 new defect
Scheme.is_projective() should use mathematical definition
Reported by: | novoselt | Owned by: | AlexGhitza |
---|---|---|---|
Priority: | major | Milestone: | sage-6.4 |
Component: | algebraic geometry | Keywords: | |
Cc: | minz | Merged in: | |
Authors: | Reviewers: | ||
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: | todo |
Description
The current implementation of is_projective
in
sage.schemes.generic.algebraic_scheme.AlgebraicScheme
is
return self.ambient_space().is_projective()
which in turn works as
def is_projective(self): """ Return whether this ambient space is projective n-space. EXAMPLES:: sage: AffineSpace(3,QQ).is_projective() False sage: ProjectiveSpace(3,QQ).is_projective() True """ # overloaded in the projective space derived class return False
Both are wrong. It is possible to have a projective scheme sitting in a non-projective variety, as well as an ambient space which is projective, yet it is not a projective n-space.
There are methods that rely on this behavior, so they should be fixed and the above methods changed so that they either answer the question "Is X a projective scheme?" in the mathematical sense or raise a NotImplementedError
if the answer is unknown.
Change History (6)
comment:1 Changed 8 years ago by
- Cc minz added
comment:2 Changed 6 years ago by
- Milestone changed from sage-5.11 to sage-5.12
comment:3 Changed 6 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:4 Changed 6 years ago by
- Milestone changed from sage-6.2 to sage-6.3
comment:5 Changed 5 years ago by
- Milestone changed from sage-6.3 to sage-6.4
comment:6 Changed 4 years ago by
- Stopgaps set to todo
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