#13198: old_submodule on modular symbols gives wrong answer
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Reporter: mderickx | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-5.2
Component: modular forms | Keywords:
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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The following is clearly wrong
{{{
sage: M=ModularSymbols(Gamma1(22),sign=1)
sage: S=M.cuspidal_submodule();S
Modular Symbols subspace of dimension 6 of Modular Symbols space of
dimension 25 for Gamma_1(22) of weight 2 with sign 1 and over Rational
Field
sage: S.new_submodule()
Modular Symbols subspace of dimension 4 of Modular Symbols space of
dimension 25 for Gamma_1(22) of weight 2 with sign 1 and over Rational
Field
sage: S.old_submodule()
Modular Symbols subspace of dimension 3 of Modular Symbols space of
dimension 25 for Gamma_1(22) of weight 2 with sign 1 and over Rational
Field
}}}
It's wrong because the new and the old subspace should be disjoint and
together span the whole space.
Note that the answers are as expected when using modular forms:
{{{
sage: M=ModularForms(Gamma1(22))
sage: S=M.cuspidal_submodule();S
Cuspidal subspace of dimension 6 of Modular Forms space of dimension 25
for Congruence Subgroup Gamma1(22) of weight 2 over Rational Field
sage: S.new_submodule()
Modular Forms subspace of dimension 4 of Modular Forms space of dimension
25 for Congruence Subgroup Gamma1(22) of weight 2 over Rational Field
sage: S.old_submodule()
Modular Forms subspace of dimension 2 of Modular Forms space of dimension
25 for Congruence Subgroup Gamma1(22) of weight 2 over Rational Field
}}}
Ps. I tested this using sage 5.2.alpha0
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13198>
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