Here is a completely separate issue with eigenspaces, one related to ease
of use:

sage: MS = MatrixSpace(QQ,2,2)
sage: A = MS([[0,-16],[-1,0]])
sage: A.eigenspaces()
[
(4, [
(1, -4)
]),
(-4, [
(1, 4)
])
]
sage: Ae = A.eigenspaces()
sage: v1 = Ae[0][1][0]; v2 = Ae[1][1][0]
sage: A*v1 == 4*v1
 False
sage: v1*A == 4*v1
 True

At least in the US, Av = lambda*v is the usual definition,
not vA = lambda*v (which is more common in Europe I think).


Robert Miller wrote:
> Should this behavior be happening?
>
> sage: MM = Matrix(GF(2),[[0]])
> sage: MM.eigenspaces()
>
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/home/server2/sage_notebook/worksheets/myworksheet/code/60.py",
> line 4, in <module>
>     MM.eigenspaces()
>   File "/sage-1.5/local/lib/python2.5/", line 1, in <module>
>
>   File "matrix2.pyx", line 1666, in matrix2.Matrix.eigenspaces
>   File "matrix2.pyx", line 966, in matrix2.Matrix.kernel
>   File 
> "/sage-1.5/local/lib/python2.5/site-packages/sage/modules/free_module.py",
> line 282, in VectorSpace
>     raise TypeError, "K must be a field"
> TypeError: K must be a field
>
>   


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