Opened 11 years ago

Last modified 11 years ago

#10832 closed defect

bug in simon_two_descent() — at Initial Version

Reported by: cremona Owned by: cremona
Priority: major Milestone: sage-4.7
Component: elliptic curves Keywords:
Cc: rlm, weigandt, gagansekhon Merged in:
Authors: John Cremona Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description

This is similar to, but different to, #10745.

sage: E = EllipticCurve([1,0,0,-6664,86543])
sage: E.simon_two_descent()
(2, 3, [(173 : 1943 : 1), (-73 : -394 : 1), (323/4 : 1891/8 : 1)])
sage: E.rank()
3
sage: E.gens()
[(-73 : -394 : 1), (323/4 : 1891/8 : 1), (173 : 1943 : 1)]

This is _wrong_. The rank is 2; the first point in the output has order 4. The mistake is that in discarding torsion points from the generators of E/2E, only points of exact order 2 are omitted!

Change History (1)

Changed 11 years ago by cremona

Applies to 4.6.2.rc0

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