#13633: Bug in cuspidal/eisenstein decomposition of modular symbols mod p
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Reporter: robharron | Owner:
davidloeffler
Type: defect | Status: new
Priority: major | Milestone:
sage-5.5
Component: modular forms | Resolution:
Keywords: modular symbols, mod p, eisenstein | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Description changed by robharron:
Old description:
> The following code
> {{{
> sage: ModularSymbols(Gamma0(46 * 47), 2, 1, GF(47)).eisenstein_subspace()
> }}}
> produces an ArithmeticError saying "subspace is not invariant under
> matrix". In a presumably completely related example, the code
>
> {{{
> sage: ModularSymbols(Gamma0(46 * 47), 2, 1,
> GF(47)).cuspidal_subspace().hecke_polynomial(47)
> }}}
> produces the exact same arithmetic error. I have computed examples like
> above where 46 is replaced by any N in the range 24 to 45 or 47 to 54 and
> where 47 is replaced with any prime less than 50 (not dividing N) and
> have not encountered the problem.
New description:
The following code
{{{
sage: ModularSymbols(Gamma0(46 * 47), 2, 1, GF(47)).eisenstein_subspace()
}}}
produces an ArithmeticError saying "subspace is not invariant under
matrix". In a presumably completely related example, the code
{{{
sage: ModularSymbols(Gamma0(46 * 47), 2, 1,
GF(47)).cuspidal_subspace().hecke_polynomial(47)
}}}
produces the exact same arithmetic error. I have computed examples like
above where 46 is replaced by any N in the range 24 to 45 or 47 to 54 and
where 47 is replaced with any prime p less than 50 (not dividing N) and
have not encountered the problem.
'''Update:''' I get the same problem when N = 60 and p is 43 or 47.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13633#comment:1>
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