#17283: Dimension mismatch in cuspidal_submodule()
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Reporter: pbruin | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.4
Component: modular forms | Resolution:
Keywords: modular symbols dimension | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by pbruin:
Old description:
> In the following example, two ways of computing the dimension of a space
> of modular symbols do not give the same result:
> {{{
> sage: k.<i> = QuadraticField(-1)
> sage: G = DirichletGroup(192)
> sage: chi = G([i,-1,-1])
> sage: M = ModularSymbols(chi);
> sage: M.cuspidal_submodule()
> AssertionError: According to dimension formulas the cuspidal subspace of
> "Modular Symbols space of dimension 0 and level 192, weight 2, character
> [zeta4, 1, -1], sign 0, over Cyclotomic Field of order 4 and degree 2"
> has dimension 40; however, computing it using modular symbols we obtained
> 0, so there is a bug (please report!).
> }}}
New description:
In the following example, two ways of computing the dimension of a space
of modular symbols do not give the same result:
{{{
sage: k.<i> = QuadraticField(-1)
sage: G = DirichletGroup(192)
sage: chi = G([i,-1,-1])
sage: M = ModularSymbols(chi);
sage: M.cuspidal_submodule()
AssertionError: According to dimension formulas the cuspidal subspace of
"Modular Symbols space of dimension 0 and level 192, weight 2, character
[zeta4, 1, -1], sign 0, over Cyclotomic Field of order 4 and degree 2" has
dimension 40; however, computing it using modular symbols we obtained 0,
so there is a bug (please report!).
}}}
The following problem is probably related (the conductor and the image of
133 are wrong in `M.character()`):
{{{
sage: chi
Dirichlet character modulo 192 of conductor 48 mapping 127 |--> zeta16^4,
133 |--> -1, 65 |--> -1
sage: M.character()
Dirichlet character modulo 192 of conductor 24 mapping 127 |--> zeta4, 133
|--> 1, 65 |--> -1
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/17283#comment:1>
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