#8451: improve galois representation for elliptic curves
-------------------------------+--------------------------------------------
   Reporter:  wuthrich         |       Owner:  cremona                          
                    
       Type:  defect           |      Status:  needs_review                     
                    
   Priority:  major            |   Milestone:  sage-4.5.3                       
                    
  Component:  elliptic curves  |    Keywords:  elliptic curves, galois 
representation, is_surjective
     Author:  Chris Wuthrich   |    Upstream:  N/A                              
                    
   Reviewer:                   |      Merged:                                   
                    
Work_issues:                   |  
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Changes (by wuthrich):

  * status:  needs_work => needs_review


Comment:

 Six months later I took the time to revise this patch completely. I have
 rewritten the function image_type. It now never gives a probabilistic
 answer, but only proven results. The package by Andrew Sutherland #8617
 will add a much better probabilistic algorithm anyway.

 One couls go on and implement things better so that a actually group is
 returned, but I do not want to waste more time on this.

 The above counter-examples now work. (I had programmed it quite badly).
 See the doctest. Also I added more documentation in the source code.

 There might still be bugs in it. It would be best though to put it in as
 such and then once #8451 is in and has a good interface, we could run test
 against it. That would be the best test.
 By now it already improves a lot (and removes some bugs in is_surjective
 that have implications to bsd stuff.

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8451#comment:13>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
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