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Bidiagonal decompositions of oscillating systems of vectors

Authors
Journal
Linear Algebra and its Applications
0024-3795
Publisher
Elsevier
Publication Date
Volume
428
Identifiers
DOI: 10.1016/j.laa.2007.12.002
Keywords
  • Totally Positive Matrix
  • Eigenvectors
  • Variation Diminishing Property

Abstract

Abstract We establish necessary and sufficient conditions, in the language of bidiagonal decompositions, for a matrix V to be an eigenvector matrix of a totally positive matrix. Namely, this is the case if and only if V and V - T are lowerly totally positive. These conditions translate into easy positivity requirements on the parameters in the bidiagonal decompositions of V and V - T . Using these decompositions we give elementary proofs of the oscillating properties of V. In particular, the fact that the jth column of V has j - 1 changes of sign. Our new results include the fact that the Q matrix in a QR decomposition of a totally positive matrix belongs to the above class (and thus has the same oscillating properties).

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