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eigenvalues of matrices in AA

asked 2015-03-27 04:41:04 -0500

Jaume gravatar image

updated 2015-03-27 08:48:20 -0500

tmonteil gravatar image
M=matrix(AA,[[0,-1],[1,0]])
M.eigenvectors_right()

raises an error "eigenvectors are not implemented for matrices with eigenvalues that are not in the fraction field of the base ring or in QQbar" which is just wrong because the eigenvalues of M are certainly in QQbar.

Can someone please explain how to avoid this problem?

Thanks,

Jaume

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answered 2015-03-27 08:22:54 -0500

tmonteil gravatar image

updated 2015-03-27 10:38:38 -0500

Thanks for reporting, this is now trac ticket 18071 .There seems that eigenvectors_right() is not implemented for the real algebraic field AA. The workaround is to define your matrix in QQbar:

sage: M = M.change_ring(QQbar)
sage: M.eigenvectors_right()
[(1*I, [
  (1, -1*I)
  ], 1), (-1*I, [
  (1, 1*I)
  ], 1)]

It also works in ZZ:

sage: M = M.change_ring(ZZ)
sage: M.eigenvectors_right()
[(-1*I, [(1, 1*I)], 1), (1*I, [(1, -1*I)], 1)]
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Asked: 2015-03-27 04:41:04 -0500

Seen: 77 times

Last updated: Mar 27 '15