#9927: non-squarefree Hecke operators on BrandtModule
-----------------------------+----------------------------------------------
Reporter: AlexGhitza | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-4.6.1
Component: modular forms | Keywords: brandt module, hecke operator
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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This was reported by Nicolás Sirolli on sage-nt:
{{{BrandtModule}}} has a problem when calculating the n-th Hecke operator
when n is not squarefree, and is smaller than the prime where the
algebra ramifies.
For example, I get a "not implemented" error if I run this
{{{
sage: B=BrandtModule(13)
sage: B.hecke_matrix(4)
}}}
Gonzalo Tornaría told me that the 'direct' algorithm is not
implemented when n is not squarefree; hence I found that
{{{
sage: B.hecke_matrix(4,algorithm='brandt')
}}}
instead, there is no trouble. A workaround could be (I'm not sure
whether this is the best to do) changing line 852 of brandt.py,
{{{
if self.level().gcd(n) != 1:
}}}
for
{{{
if self.level().gcd(n) != 1 or is_squarefree(n)==False:
}}}
(and adding {{{is_squarefree}}} to the "imports" block).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9927>
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