#12879: TestSuite failures for HeckeModule Homsets
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Reporter: nthiery | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-5.3
Component: modular forms | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
Here is one particularly nasty thing. I stored some objects involved in
errors. Reloading them, I find the following in a patched version (as
suggested above):
{{{
sage: A = load("/home/king/SAGE/work/categories/modformA")
sage: B = load("/home/king/SAGE/work/categories/modformB")
sage: A
Modular Symbols space of dimension 3 and level 5, weight 7, character [i],
sign 1, over Number Field in c with defining polynomial x^2 - 402*i over
its base field
sage: B
Modular Symbols space of dimension 3 and level 5, weight 7, character [i],
sign 1, over Number Field in i with defining polynomial x^2 + 1
sage: A.boundary_space().dimension()
0
sage: K.<i> = QuadraticField(-1)
sage: x = polygen(K); L.<c> = K.extension(x^2 - 402*i)
sage: chi = DirichletGroup(5, K).gen(0)
sage: N = Newforms(chi, 7, base_ring = L)
sage: Newforms(chi, 7, names='a')
Traceback (most recent call last):
...
TypeError: Unable to coerce x (=[-1]
[-1]
[-1]) to a morphism in Set of Morphisms from Modular Symbols space of
dimension 3 and level 5, weight 7, character [i], sign 1, over Number
Field in i with defining polynomial x^2 + 1 to Boundary Modular Symbols
space of level 5, weight 7, character [i] and dimension 1 over Number
Field in c with defining polynomial x^2 - 402*i over its base field in
Category of commutative additive groups
sage: A.boundary_space().dimension()
1
}}}
Hence, `A.boundary_space()` used to be of dimension zero, but during the
computation, it is turned into dimension one!
That does not happen without the patch:
{{{
sage: A = load("/home/king/SAGE/work/categories/modformA")
sage: B = load("/home/king/SAGE/work/categories/modformB")
sage: A.boundary_space().dimension()
0
sage: K.<i> = QuadraticField(-1)
sage: x = polygen(K); L.<c> = K.extension(x^2 - 402*i)
sage: chi = DirichletGroup(5, K).gen(0)
sage: N = Newforms(chi, 7, base_ring = L)
sage: Newforms(chi, 7, names='a')
[q + a0*q^2 + (i*a0 - 5*i + 5)*q^3 + ((-5*i - 5)*a0 + 24*i)*q^4 + ((10*i -
5)*a0 - 40*i - 55)*q^5 + O(q^6)]
sage: A.boundary_space().dimension()
0
}}}
Further digging reveals: `A.boundary_space().dimension()` is indeed
''not'' constant! It relies on a list of known generators, that may grow.
But with my patch, the homset assumes that the dimensions are constant.
Bad me.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12879#comment:3>
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