#12188: Bug in is_smooth for curves over CC
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Reporter: johanbosman | Owner: AlexGhitza
Type: defect | Status: new
Priority: critical | Milestone: sage-5.4
Component: algebraic geometry | Resolution:
Keywords: singular | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
A quick test reveals that:
{{{
P.<X,Y,Z> = CC[]
C = Curve(X)
self = C
d = self.codimension()
minors = self.Jacobian_matrix().minors(d)
I = self.defining_ideal()
minors = tuple([ I.reduce(m) for m in minors ])
}}}
(Who ever thought that "Jacobian" was a good name for the singular
subscheme? I think most algebraic geometers expect something else when
they ask for the Jacobian of a curve).
and a little look indeed shows that this code tries to use "singular"'s
reduce (the ideal gets reconstructed several times), and I think it does
so successfully (does singular now allow rings with float coefficients?),
so it looks indeed like a mismatch in ring deletions. It may be a good
test case, because the ring really gets constructed internally, via a
`_singular_` method.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12188#comment:5>
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