#15434: elliptic curve isogenies: follow-up to #13615
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Reporter: cremona | Owner:
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.13
Component: elliptic curves | Resolution:
Keywords: | Merged in:
Authors: John Cremona | Reviewers: Volker Braun
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by cremona):
* status: positive_review => needs_work
Comment:
Not so fast: my patch is not good on non-short Weierstrass models. Warren
now reports this:
{{{
sage: K.<i> = NumberField(x^2+1)
sage: E = EllipticCurve(K, [-2*i-1,0])
sage: E.isogenies_prime_degree(17)
[Isogeny of degree 17 from Elliptic Curve defined by y^2 = x^3 +
(-2*i-1)*x over Number Field in i with defining polynomial x^2 + 1 to
Elliptic Curve defined by y^2 = x^3 + (-82*i-641)*x over Number Field in i
with defining polynomial x^2 + 1,
Isogeny of degree 17 from Elliptic Curve defined by y^2 = x^3 + (-2*i-1)*x
over Number Field in i with defining polynomial x^2 + 1 to Elliptic Curve
defined by y^2 = x^3 + (-562*i+319)*x over Number Field in i with defining
polynomial x^2 + 1]
sage: E.global_minimal_model().isogenies_prime_degree(17)
<boom>
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/15434#comment:4>
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