On the Mazur-Orlicz theorem
It is shown that the sum and the product of two commuting Banach space operators with Dunford’s property have the single-valued extension property.
Let be a bounded operator on a complex Banach space . If is an open subset of the complex plane such that is of Kato-type for each , then the induced mapping has closed range in the Fréchet space of analytic -valued functions on . Since semi-Fredholm operators are of Kato-type, this generalizes a result of Eschmeier on Fredholm operators and leads to a sharper estimate of Nagy’s spectral residuum of . Our proof is elementary; in particular, we avoid the sheaf model of Eschmeier and...
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