#11474: Elliptic curves should be unique parent structures
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       Reporter:  SimonKing        |        Owner:  cremona
           Type:  defect           |       Status:  needs_info
       Priority:  major            |    Milestone:  sage-6.2
      Component:  elliptic curves  |   Resolution:
       Keywords:  unique parent    |    Merged in:
        Authors:  Simon King       |    Reviewers:
Report Upstream:  N/A              |  Work issues:
         Branch:                   |       Commit:
   Dependencies:                   |     Stopgaps:
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Comment (by cremona):

 I agree with Peter here (we have been discussing these issues in our
 common room in Warwick).

 I particularly want to emphasize that what you have in mind is quite a
 large project, which needs to be done step by step, with plenty of input
 from other experienced Sage users who will be greatly affected by such
 changes (e.g. me!).  Also, be careful that the improved design will not be
 accompanied by a decrease in efficiency.

 Some of what is being proposed here would have been done a lot earlier,
 but Sage's support for f.g. abelian groups was not good enough in the
 early days.  As soon as it became good enough it was applied to the
 simplest of these cases, namely the group of points of an e.c. over a
 finite field.

 We want to keep separate the abstract abelian group from the concrete
 realization of it as a set of points, so that we can use generaic abelian
 group functionality to (for example) compute kernels.  And as well as the
 easy map from the abstract group to the concrete point set (using known
 generators) we must also provide the harder map in the reverse direction,
 which is a form of elliptic logarithm.  This is actually easier in the
 number field case since we can use canonical heights to express a point as
 a linear combination of the generators.

--
Ticket URL: <http://trac.sagemath.org/ticket/11474#comment:17>
Sage <http://www.sagemath.org>
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