#8945: Cremona labels messed up
-----------------------------+----------------------------------------------
Reporter: davidloeffler | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-4.6
Component: modular forms | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by cremona):
One way of dealing with this would be as follows: for levels up to 130000
and weight 2 newforms for Gamma_0(N), the decomposition function could
sort the forms according to the sorting of the curves in the database.
This would be a real pain to do (though only once!) since -- as I pointed
out earlier -- there is no simple way to do this for levels < 450 or so.
All one needs is a slave to work out around 400 cases like this:
{{{
sage: [EllipticCurve('225'+l).aplist(20) for l in 'abcde']
[[0, 0, 0, -5, 0, -5, 0, -1], [0, 0, 0, 5, 0, 5, 0, -1], [-1, 0, 0, 0, 4,
2, 2, 4], [2, 0, 0, 3, -2, -1, 2, -5], [-2, 0, 0, -3, -2, 1, -2, -5]]
sage: [[Newform('225'+l,names='a')[p] for p in prime_range(20)] for l in
'cdbea']
[[0, 0, 0, -5, 0, -5, 0, -1], [0, 0, 0, 5, 0, 5, 0, -1], [-1, 0, 0, 0, 4,
2, 2, 4], [2, 0, 0, 3, -2, -1, 2, -5], [-2, 0, 0, -3, -2, 1, -2, -5]]
}}}
so as far as level 225 is concerned, 'cdbea' does the trick.
In eclib's src/g0n/curvesort.cc there are lots of lines like this:
{{{
case 222: return EDACB[form]; break;
}}}
where
{{{
int EDACB[] = {4,3,0,2,1};
}}}
which I tediously worked out by hand around 20 years ago...
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8945#comment:4>
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