Summary
In this note, the minimal Gerschgorin setG is defined for a matrixA, relative to a matrixD and a familyF of norms. This minimal Gerschgorin set is shown to be an inclusion region for the eigenvalues of a related collection\(\widehat\Omega \) of matrices, i.e.,
The main result is a necessary and sufficient condition for equality to hold in the above inclusion. In addition, examples are given, one for which equality does not hold in the above inclusion.
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Research supported in part by the Atomic Energy Commission under Grant AT (11-1)-2075.
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Varga, R.S., Levinger, B.W. On minimal Gerschgorin sets for families of norms. Numer. Math. 20, 252–256 (1973). https://doi.org/10.1007/BF01436567
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DOI: https://doi.org/10.1007/BF01436567