#7907: Bug in characteristic 2 isogenies of degree >3
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Reporter: cremona | Owner: cremona
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.1
Component: elliptic curves | Keywords: isogeny
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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Comment(by cremona):
Here's an example of the failure which will be put into a doctest in the
patch.
Before:
{{{
sage: F = GF(128,'a')
sage: a = F.gen()
sage: E = EllipticCurve([1,0,0,0,(a**6+a**4+a**2+a)])
sage: x = polygen(F)
sage: ker = (x^6 + (a^6 + a^5 + a^4 + a^3 + a^2 + a)*x^5 + (a^6 + a^5 +
a^2 + 1)*x^4 + (a^6 + a^5 + a^4 + a^3 + a^2 + 1)*x^3 + (a^6 + a^3 + a)*x^2
+ (a^4 + a^3 + 1)*x + a^5 + a^4 + a)
sage: E.isogeny(ker)
Traceback (most recent call last):
...
NameError: global name 'binomial' is not defined
}}}
After:
{{{
sage: F = GF(128,'a')
sage: a = F.gen()
sage: E = EllipticCurve([1,0,0,0,(a**6+a**4+a**2+a)])
sage: x = polygen(F)
sage: ker = (x^6 + (a^6 + a^5 + a^4 + a^3 + a^2 + a)*x^5 + (a^6 + a^5 +
a^2 + 1)*x^4 + (a^6 + a^5 + a^4 + a^3 + a^2 + 1)*x^3 + (a^6 + a^3 + a)*x^2
+ (a^4 + a^3 + 1)*x + a^5 + a^4 + a)
sage: E.isogeny(ker)
Isogeny of degree 13 from Elliptic Curve defined by y^2 + x*y = x^3 +
(a^6+a^4+a^2+a) over Finite Field in a of size 2^7 to Elliptic Curve
defined by y^2 + x*y = x^3 + (a^6+a^5+a^4+a^3+a^2+a)*x + (a^5+a^3) over
Finite Field in a of size 2^7
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7907#comment:2>
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