#14060: Improve minimal_quadratic_twist()
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Reporter: cremona | Owner: cremona
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.1
Component: elliptic curves | Resolution:
Keywords: pari precision | Merged in:
Authors: John Cremona | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/cremona/ticket/14060 | dc07e494c5230bef1dd7e1a0df351194a03acb36
Dependencies: | Stopgaps:
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Changes (by {'newvalue': u'John Cremona', 'oldvalue': ''}):
* status: new => needs_review
* commit: => dc07e494c5230bef1dd7e1a0df351194a03acb36
* author: => John Cremona
Old description:
> We need a better implementation of minimal_quadratic_twist(), for example
> if the conductor is square-free then there is no need to do so much work
> as is currently done. Additionally, when j(E)=0 or 1728 the curve
> returned is a minimal twist, but not necessarily a quadratic twist, so
> the documentation (or function name, or something) needs correcting.
New description:
We need a better implementation of minimal_quadratic_twist(), for example
if the conductor is square-free then there is no need to do so much work
as is currently done. Additionally, when j(E)=0 or 1728 the curve
returned is a minimal quadratic twist, but not necessarily the minimal
twist, and it would be a good thing for the documentation to make this
clear.
--
Comment:
I have implemented the small improvement (do nothing if the conductor is
square-free) with a new doctest, and also expanded on the documentation in
the exceptional cases j=0, 1728 to remove any confusion, with an example!
I decided not to implement a new {{{minimal_twist()}}} function since
{{{
EllipticCurve(j=E.j_invariant())
}}}
does that. But I could.
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Last 10 new commits:
||[http://git.sagemath.org/sage.git/commit/?id=520cfca7cdd1734c1694a63abb3b74b654f7cfb5
520cfca]||{{{Merge branch 'master' of git://github.com/sagemath/sage into
build_system}}}||
||[http://git.sagemath.org/sage.git/commit/?id=38d22b794f2febb5ad4cfcebdfebcd4be60f4c93
38d22b7]||{{{Merge branch 'master' of ssh://trac.sagemath.org:2222/sage
into build_system}}}||
||[http://git.sagemath.org/sage.git/commit/?id=139dcf5c9eed42069d260cf01f52ce84032038ac
139dcf5]||{{{Merge branch 'build_system' of git://github.com/sagemath/sage
into build_system}}}||
||[http://git.sagemath.org/sage.git/commit/?id=17e17ddc5bae00a52ed1eeb69d2518bb05e5c9f7
17e17dd]||{{{Merge branch 'master' of ssh://trac.sagemath.org:2222/sage
into build_system}}}||
||[http://git.sagemath.org/sage.git/commit/?id=b06bd7c4c0b22d891023a30fc10ec4d2dd33a4ab
b06bd7c]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
||[http://git.sagemath.org/sage.git/commit/?id=858bb9582d4e7bff3ab6dc5572d1d14a32cae6f7
858bb95]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
||[http://git.sagemath.org/sage.git/commit/?id=0523e0ddae40720246f5b357c09e78fa88d4671a
0523e0d]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
||[http://git.sagemath.org/sage.git/commit/?id=88ffd55b76c68cc1b462c6fe473545d8856d1464
88ffd55]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
||[http://git.sagemath.org/sage.git/commit/?id=68d0a5d1f1852db83b575d3ac93210cb291ad84f
68d0a5d]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
||[http://git.sagemath.org/sage.git/commit/?id=057b3cda7e5b1c7f11d94506197e196c7a492d54
057b3cd]||{{{Merge branch 'master' of git://github.com/sagemath/sage}}}||
--
Ticket URL: <http://trac.sagemath.org/ticket/14060#comment:8>
Sage <http://www.sagemath.org>
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