#6925: Fast way of calculating cuspidal subgroup of J0(N)
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Reporter: syazdani | Owner: tbd
Type: enhancement | Status:
Priority: major | needs_review
Component: modular forms | Milestone: sage-5.13
Keywords: cuspidal subgroup, modular | Resolution:
abelian variety | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by chapoton:
Old description:
> This is the first implementation of Ligozat's method of calculating the
> rational cuspidal subgroup of J_0(N). This is done by doing linear
> algebra in d(N)*d(N) matrices, which seems considerably faster than the
> modular symbol methods.
>
> This code is functional at this point. The problems with it are
>
> a) __cmp__ is not called.
>
> b) Hecke operators aren't defined yet.
>
> c) can't coerce specific degree zero cuspidal divisors in our group.
>
> Apply:
>
> * [attachment:6925-rationalcuspidal.patch]
> * [attachment:trac_6925_addon1.patch]
New description:
This is the first implementation of Ligozat's method of calculating the
rational cuspidal subgroup of J_0(N). This is done by doing linear algebra
in d(N)*d(N) matrices, which seems considerably faster than the modular
symbol methods.
This code is functional at this point. The problems with it are
a) __cmp__ is not called.
b) Hecke operators aren't defined yet.
c) can't coerce specific degree zero cuspidal divisors in our group.
Apply:
* [attachment:trac-6925-rationalcuspidal-rebased-v1.patch]
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Ticket URL: <http://trac.sagemath.org/ticket/6925#comment:22>
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