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Re:Clojure Linear Algebra Refresher: Eigenvalues and Eigenve... by kgwgk on Tuesday June 06, 2017 @01:10PM (#14498918)
The problem arises when there is degeneration (some eigenvalues are repeated). See for example https://www.ch.ntu.edu.tw/~byjin/course/ChemMath/handouts/de...

[edit: the rest of my original comment was not correct]

If an eigenvalue is unique, the corresponding eigenvectors are on a line. If it appears twice, the corresponding eigenvectors are [edit: could be] on a plane. In general, they span [edit: could span] a subspace of dimension equal to the multiplicity.

Re:Clojure Linear Algebra Refresher: Eigenvalues and Eigenve... by neutronicus on Tuesday June 06, 2017 @01:32PM (#14499143)
The dimension of the space spanned by the eigenvectors associated with a degenerate eigenvalue is bounded above by the algebraic multiplicity of the eigenvalue and bounded below by one.
Re:Clojure Linear Algebra Refresher: Eigenvalues and Eigenve... by btilly on Tuesday June 06, 2017 @01:28PM (#14499101)
Not true. The matrix [[1 1] [0 1]] has the eigenvalue 1 repeated twice but the eigenvectors are on a line.

The generalized eigenvectors are on a plane.

The case where the eigenvectors do not span the space corresponds to matrices whose Jordan normal form has upper triangular bits.