#13158 closed defect (fixed)
Local components bug finding minimal twist
Reported by: | davidloeffler | Owned by: | craigcitro |
---|---|---|---|
Priority: | minor | Milestone: | sage-6.4 |
Component: | modular forms | Keywords: | local components |
Cc: | Merged in: | ||
Authors: | David Loeffler | Reviewers: | Frédéric Chapoton |
Report Upstream: | N/A | Work issues: | |
Branch: | 3577e02 (Commits, GitHub, GitLab) | Commit: | |
Dependencies: | Stopgaps: |
Description
The following is from an email of François Brunault:
I got the following error when trying to compute minimal twists in Sage. Here f is the newform attached to the elliptic curve 256a1, and the minimal twist of f has level 64.
Best, François
sage: f=Newforms(256,names='a')[0] sage: T=TypeSpace(f,2) sage: T.is_minimal() False sage: T.minimal_twist() --------------------------------------------------------------------------- ValueError Traceback (most recent call last) /Users/francoisbrunault/<ipython console> in <module>() /Users/francoisbrunault/Documents/SAGE/sage-5.0.beta13/local/lib/python2.7/site-packages/sage/modular/local_comp/type_space.pyc in minimal_twist(self) 383 D._set_sign(D.star_eigenvalues()[0]) 384 M = ModularForms(D.group(), D.weight()) --> 385 ff = Newform(M, D, names='a') 386 return ff 387 /Users/francoisbrunault/Documents/SAGE/sage-5.0.beta13/local/lib/python2.7/site-packages/sage/modular/modform/element.pyc in __init__(self, parent, component, names, check) 636 raise ValueError, "component must be cuspidal" 637 if not component.is_simple(): --> 638 raise ValueError, "component must be simple" 639 extension_field = component.eigenvalue(1,name=names).parent() 640 if extension_field != parent.base_ring(): # .degree() != 1 and rings.is_NumberField(extension_field): ValueError: component must be simple
Change History (10)
comment:1 Changed 8 years ago by
- Milestone changed from sage-5.11 to sage-5.12
comment:2 Changed 8 years ago by
- Milestone changed from sage-6.1 to sage-6.2
comment:3 Changed 7 years ago by
- Milestone changed from sage-6.2 to sage-6.3
comment:4 Changed 7 years ago by
- Milestone changed from sage-6.3 to sage-6.4
comment:5 Changed 6 years ago by
- Branch set to u/davidloeffler/local_components_bug_finding_minimal_twist
comment:6 Changed 6 years ago by
- Commit set to 1994692c566e53f79774947647a03ab3c2042b98
- Status changed from new to needs_review
comment:7 Changed 6 years ago by
- Branch changed from u/davidloeffler/local_components_bug_finding_minimal_twist to public/ticket/13158
- Commit changed from 1994692c566e53f79774947647a03ab3c2042b98 to 3577e02d18bf8e0a449c82d88880ea6e62de3a88
- Reviewers set to Frédéric Chapoton
- Status changed from needs_review to positive_review
comment:8 Changed 6 years ago by
Thanks for the review! The patchbot seems a bit confused, but I'm sure it'll catch up shortly :-)
comment:9 Changed 6 years ago by
- Branch changed from public/ticket/13158 to 3577e02d18bf8e0a449c82d88880ea6e62de3a88
- Resolution set to fixed
- Status changed from positive_review to closed
comment:10 Changed 6 years ago by
- Commit 3577e02d18bf8e0a449c82d88880ea6e62de3a88 deleted
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Somehow, this sat idle for 3 years despite the fact that the fix is about 2 lines! It turns out that the code relies on the assumption that the trace of the type space down to the minimal level is simple, but if f is of CM type it can be the direct sum of two simple modules of opposite sign.
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Trac 13158: local components bug finding minimal twist