Operator Radii and Unitary Operators
نویسندگان
چکیده
Let ρ ≥ 1 and w ρ (A) be the operator radius of a linear operator A. Suppose m is a positive integer. It is shown that for a given invertible linear operator A acting on a Hilbert space, one has w ρ (A −m) ≥ w ρ (A) −m. The equality holds if and only if A is a multiple of a unitary operator.
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