Opened 10 years ago
Closed 9 years ago
#13593 closed enhancement (fixed)
tighter upper bound on elliptic curve rank
Reported by: | ohanar | Owned by: | cremona |
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Priority: | major | Milestone: | sage-6.1 |
Component: | elliptic curves | Keywords: | |
Cc: | aly.deines | Merged in: | |
Authors: | R. Andrew Ohana, Chris Wuthrich | Reviewers: | John Cremona |
Report Upstream: | N/A | Work issues: | |
Branch: | u/wuthrich/ticket/13593 (Commits, GitHub, GitLab) | Commit: | bf7617dbf1778300f421ca0e0305d881a0c8bda2 |
Dependencies: | Stopgaps: |
Description (last modified by )
[See #15608 for a list of open simon_two_descent tickets]
The current upper bound in rank_bounds
do not take into account two torsion. This corrects this and thus gives a tighter upper bound.
Attachments (1)
Change History (17)
Changed 10 years ago by
Attachment: | trac13593.patch added |
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comment:1 Changed 10 years ago by
Description: | modified (diff) |
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Status: | new → needs_review |
comment:2 follow-up: 3 Changed 10 years ago by
Status: | needs_review → needs_work |
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comment:3 Changed 10 years ago by
Replying to ohanar:
need to fix doctests...
Update: well having trouble finding a new example where the bounds disagree -- guess this is what I get for trying to improve something :)
I do think that Simon's scripts already take 2-torsion into account, even though he returns 2-torsion points in the list of gens (which I remember filtering out). Needs checking though.
comment:4 Changed 10 years ago by
If I recall, the upper bound is supposed to be a bound on the rank of the 2-Selmer group, which would not take into account 2-torsion -- unless I'm being totally stupid, which could very well be the case considering how new I am to this stuff :).
comment:5 Changed 9 years ago by
Milestone: | sage-5.11 → sage-5.12 |
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comment:6 Changed 9 years ago by
A simple example:
sage: K.<i> = NumberField(x^2+1) sage: E = EllipticCurve([2+3*i,0]) sage: E.simon_two_descent() (0, 1, [(0 : 0 : 1), (0 : 0 : 1)]) sage: E.rank_bounds() (0, 1) sage: Em = magma(E) sage: Em.TwoSelmerGroup() Abelian Group isomorphic to Z/2 ...
Simon's script returns indeed as the second argument the dimension of the 2-Selmer group and currently rank_bounds
copies that. So the supposed change here is indeed good. However, we need to add an example in the doctest, too.
Furthermore, I will correct a few other things there, while I am at it.
comment:7 Changed 9 years ago by
Branch: | → u/wuthrich/ticket/13593 |
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Created: | Oct 11, 2012, 11:28:04 PM → Oct 11, 2012, 11:28:04 PM |
Modified: | Dec 28, 2013, 12:56:43 AM → Dec 28, 2013, 12:56:43 AM |
comment:8 Changed 9 years ago by
Authors: | R. Andrew Ohana → R. Andrew Ohana, Chris Wuthrich |
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Commit: | → 9a069c7225480773cd6429e87f10bf5d0d8855e0 |
Status: | needs_work → needs_review |
I also corrected the documentation - it was quite bad ! Meaning mathematically incorrect. Hope it is better now.
At some point we will want to filter out generators for E(K)/2E(K) - or even E(K). However, I left for now to return all points that Simon's script finds.
New commits:
9a069c7 | Trac #13593: ranks of elliptic curves over number fields
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comment:9 Changed 9 years ago by
Description: | modified (diff) |
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Priority: | minor → major |
... and then I spotted that the list may contain points of order 2. the second commit filters the torsion points out of the list.
comment:10 Changed 9 years ago by
Commit: | 9a069c7225480773cd6429e87f10bf5d0d8855e0 → b1550dc0081c5d6cb971af025108cacf653b5fa8 |
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Branch pushed to git repo; I updated commit sha1. New commits:
b1550dc | Trac 13593: Do not put torsion points into gens.
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comment:13 Changed 9 years ago by
Commit: | b1550dc0081c5d6cb971af025108cacf653b5fa8 → bf7617dbf1778300f421ca0e0305d881a0c8bda2 |
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Branch pushed to git repo; I updated commit sha1. New commits:
bf7617d | spelling error
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comment:14 Changed 9 years ago by
Description: | modified (diff) |
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comment:15 Changed 9 years ago by
Reviewers: | → John Cremona |
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Status: | needs_review → positive_review |
I looked at all three commits and approve of what they do. Test pass -- positive review.
comment:16 Changed 9 years ago by
Resolution: | → fixed |
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Status: | positive_review → closed |
need to fix doctests...
Update: well having trouble finding a new example where the bounds disagree -- guess this is what I get for trying to improve something :)