#6384: elliptic curve -- isogeny function is not robust -- it doesn't check
validity of its input
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Reporter: was | Owner: shumow
Type: defect | Status: new
Priority: major | Milestone: sage-4.1
Component: algebra | Keywords:
Reviewer: | Author:
Merged: |
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Comment(by wuthrich):
I would change the input to be as now, but if a list of points is given,
the kernel is understood to be the subgroup '''GENERATED''' by these
points.
I guess one needs to check the following:
* If a list of points is given that they are torsion.
* If a polynomial of degree n is given that it divides the
division_polynomial(2*n+1). Also the polynomial should be squarefree, i.e.
define a reduced scheme.
Am I right ?
Why is the kernel_polynomial a multivariable polynomial ?
Also as an enhancement we could have simply an integer to get the
multiplication by n as an isogeny. And for curves over QQ, a
codomain=label (and the degree can be read off the isogeny_class matrix).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6384#comment:3>
Sage <http://sagemath.org/>
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