#15890: EllipticCurve_number_field.is_isogenous() raises error for non-minimal
models
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Reporter: pbruin | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.2
Component: elliptic curves | Keywords: isogeny number field
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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The following error is due to `EllipticCurve_number_field.is_isogenous()`
not changing to a local minimal model before reducing.
{{{
sage: K.<s>=QuadraticField(229)
sage: c4=2173-235*(1-s)/2
sage: c6=-124369+15988*(1-s)/2
sage: c4c=2173-235*(1+s)/2
sage: c6c=-124369+15988*(1+s)/2
sage: E=EllipticCurve_from_c4c6(c4, c6)
sage: Ec=EllipticCurve_from_c4c6(c4c, c6c)
sage: E.conductor()
Fractional ideal (1)
sage: K.ideal(E.discriminant()).factor()
(Fractional ideal (3, 1/2*s + 1/2))^12 # not minimal at this prime
sage: E.is_isogenous(Ec)
...
ArithmeticError: Invariants [0, 0, 0, 0, 0] define a singular curve.
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/15890>
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