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Numerical ranges and matrix completions
Journal article   Peer reviewed

Numerical ranges and matrix completions

D.W. Hadwin, K.J. Harrison and J.A. Ward
Linear Algebra and its Applications, Vol.315(1-3), pp.145-154
2000
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Abstract

There are two natural ways of defining the numerical range of a partial matrix. We show that for each partial matrix supported on a given pattern they give the same convex subset of the complex plane if and only if a graph associated with the pattern is chordal. This extends a previously known result (C.R. Johnson, M.E. Lundquist, Operator Theory: Adv. Appl. 50 (1991) 283–291) to patterns that are not necessarily reflexive and symmetric, and our proof overcomes an apparent gap in the proof given in the above-mentioned reference. We also define a stronger completion property that we show is equivalent to the pattern being an equivalence.

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Citation topics
9 Mathematics
9.50 Applied Statistics & Probability
9.50.1025 Operator Theory
Web Of Science research areas
Mathematics
Mathematics, Applied
ESI research areas
Mathematics
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