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Max-min and min-max approximation problems for normal matrices revisited. (English) Zbl 1296.90136

Summary: We give a new proof of an equality of certain max-min and min-max approximation problems involving normal matrices. The previously published proofs of this equality apply tools from matrix theory, (analytic) optimization theory, and constrained convex optimization. Our proof uses a classical characterization theorem from approximation theory and thus exploits the link between the two approximation problems with normal matrices on the one hand and approximation problems on compact sets in the complex plane on the other.

MSC:

90C47 Minimax problems in mathematical programming
49K35 Optimality conditions for minimax problems
65F10 Iterative numerical methods for linear systems

Software:

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