#14476: non-integral models can cause a bug in local_data for elliptic curves
over
number fields
---------------------------+-----------------------------------------------
Reporter: | Owner: cremona
wuthrich | Status: positive_review
Type: defect | Milestone: sage-5.12
Priority: major | Resolution:
Component: | Merged in:
elliptic curves | Reviewers: Frédéric Chapoton, John Cremona
Keywords: | Work issues:
local_data | Commit:
Authors: Chris | Stopgaps:
Wuthrich |
Report Upstream: N/A |
Branch: |
Dependencies: |
---------------------------+-----------------------------------------------
Changes (by chapoton):
* status: needs_info => positive_review
Old description:
> This example was spotted by Dino Lorenzini:
>
> {{{
> sage: t = QQ['t'].0
> sage: K.<g> = NumberField(t^4 - t^3-3*t^2 - t +1)
> sage: x=-3/5*g^3 + 2/5*g^2 + 3/5*g + 4/5
> sage: y=1/15*g^3 - 3/5*g^2 + 3/5*g + 17/15
> sage: r = (x^2*y - x*y + y - 1) / (x^2*y - x)
> sage: s = (x*y - y + 1) / (x*y)
> sage: c = s*(r - 1)
> sage: b = c*r
> sage: E = EllipticCurve(K,[1-c,-b,-b,0,0])
> sage: E.local_data()
> }}}
>
> which causes a {{{TypeError}}} in {{{_reduce_local}}}.
> Tickets that may be linked to this are #11630 and #9410.
>
> '''Added later:''' Moreover I can add another bug that he showed me
>
> {{{
> sage: R.<t> = QQ[]
> sage: K.<g> = NumberField(t^4 - t^3 - 3*t^2 - t + 1)
> sage: E = EllipticCurve([ -43/625*g^3 + 14/625*g^2 - 4/625*g + 706/625,
> -4862/78125*g^3 - 4074/78125*g^2 - 711/78125*g + 10304/78125,
> -4862/78125*g^3 - 4074/78125*g^2 - 711/78125*g + 10304/78125, 0,0])
> sage: E.global_integral_model()
> }}}
>
> ends in a {{{AssertionError: bug in global_integral_model}}}.
New description:
This example was spotted by Dino Lorenzini:
{{{
sage: t = QQ['t'].0
sage: K.<g> = NumberField(t^4 - t^3-3*t^2 - t +1)
sage: x=-3/5*g^3 + 2/5*g^2 + 3/5*g + 4/5
sage: y=1/15*g^3 - 3/5*g^2 + 3/5*g + 17/15
sage: r = (x^2*y - x*y + y - 1) / (x^2*y - x)
sage: s = (x*y - y + 1) / (x*y)
sage: c = s*(r - 1)
sage: b = c*r
sage: E = EllipticCurve(K,[1-c,-b,-b,0,0])
sage: E.local_data()
}}}
which causes a {{{TypeError}}} in {{{_reduce_local}}}.
Tickets that may be linked to this are #11630 and #9410.
'''Added later:''' Moreover I can add another bug that he showed me
{{{
sage: R.<t> = QQ[]
sage: K.<g> = NumberField(t^4 - t^3 - 3*t^2 - t + 1)
sage: E = EllipticCurve([ -43/625*g^3 + 14/625*g^2 - 4/625*g + 706/625,
-4862/78125*g^3 - 4074/78125*g^2 - 711/78125*g + 10304/78125,
-4862/78125*g^3 - 4074/78125*g^2 - 711/78125*g + 10304/78125, 0,0])
sage: E.global_integral_model()
}}}
ends in a {{{AssertionError: bug in global_integral_model}}}.
APPLY:
* [attachment:trac_14476_bugs_in_local_data.patch]
* [attachment:trac_14476_trac_links.patch]
--
Comment:
both patches should be applied, as listed now at bottom of the description
--
Ticket URL: <http://trac.sagemath.org/ticket/14476#comment:16>
Sage <http://www.sagemath.org>
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