Opened 11 months ago
Closed 10 months ago
#32269 closed defect (fixed)
Isogenies prime degree fails on some CM curves
Reported by: | gh-sachihashimoto | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-9.5 |
Component: | elliptic curves | Keywords: | elliptic curves, isogeny, CM |
Cc: | alexjbest | Merged in: | |
Authors: | Alex J. Best | Reviewers: | Edgar Costa |
Report Upstream: | N/A | Work issues: | |
Branch: | 6b6dc19 (Commits, GitHub, GitLab) | Commit: | 6b6dc19fed27e3d0b5a4b529e1937986640aa14b |
Dependencies: | Stopgaps: |
Description
The code:
K.<a> = QuadraticField(-11) E = EllipticCurve(K, [0,1,0,-117,-541]) E.isogenies_prime_degree(53)
returns an empty list. But, since E has CM by the ring of integers of K, it has to have an isogeny of degree p for p splitting in K, so this doesn't make sense.
If you import isogenies_prime_degree_general from isogeny_small_degree.py then
isogenies_prime_degree_general(E,53)
correctly returns
[Isogeny of degree 53 from Elliptic Curve defined by y^2 = x^3 + x^2 + (-117)*x + (-541) over Number Field in a with defining polynomial x^2 + 11 with a = 3.316624790355400?*I to Elliptic Curve defined by y^2 = x^3 + x^2 + (98560*a+42123)*x + (-12561472*a-61946205) over Number Field in a with defining polynomial x^2 + 11 with a = 3.316624790355400?*I, Isogeny of degree 53 from Elliptic Curve defined by y^2 = x^3 + x^2 + (-117)*x + (-541) over Number Field in a with defining polynomial x^2 + 11 with a = 3.316624790355400?*I to Elliptic Curve defined by y^2 = x^3 + x^2 + (-98560*a+42123)*x + (12561472*a-61946205) over Number Field in a with defining polynomial x^2 + 11 with a = 3.316624790355400?*I]
Change History (13)
comment:1 Changed 11 months ago by
- Branch set to u/alexjbest/isog-nf
- Commit set to 96561b332f35d1e9d56b190ce4a09221b779fb29
- Status changed from new to needs_info
- Work issues set to wait for CI
comment:2 Changed 11 months ago by
- Status changed from needs_info to needs_review
comment:3 Changed 11 months ago by
- Commit changed from 96561b332f35d1e9d56b190ce4a09221b779fb29 to 251c8297a5872756256a42e7a506c95ed5a91ed8
Branch pushed to git repo; I updated commit sha1. New commits:
251c829 | output
|
comment:4 Changed 11 months ago by
comment:5 Changed 11 months ago by
LGTM, but that test with ell = 53
is not going to fly.
Why not ell = 37
? it is equally broken and takes 1/6 of the time.
comment:6 Changed 11 months ago by
@edgarcosta, right the example in code uses l=37, it might still need marking as # long time though, I'm not sure.
comment:7 Changed 11 months ago by
Upsidaisy! Ignore my comment then.
I was hoping that the patch bot would tell us what to do regarding the necessity of the marking as # long
comment:8 Changed 11 months ago by
- Commit changed from 251c8297a5872756256a42e7a506c95ed5a91ed8 to 6b6dc19fed27e3d0b5a4b529e1937986640aa14b
Branch pushed to git repo; I updated commit sha1. New commits:
6b6dc19 | fix doctest
|
comment:9 Changed 11 months ago by
- Work issues wait for CI deleted
comment:10 Changed 11 months ago by
- Status changed from needs_review to positive_review
comment:11 Changed 11 months ago by
- Reviewers set to Edgar Costa
comment:12 Changed 10 months ago by
- Milestone changed from sage-9.4 to sage-9.5
comment:13 Changed 10 months ago by
- Branch changed from u/alexjbest/isog-nf to 6b6dc19fed27e3d0b5a4b529e1937986640aa14b
- Resolution set to fixed
- Status changed from positive_review to closed
New commits:
attempt to fix 32269