On the topological boundary of semi-Fredholm operators

Skhiri, Haïkel

doi:10.1090/S0002-9939-98-04262-2

On the topological boundary of semi-Fredholm operators
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by Haïkel Skhiri PDF

Proc. Amer. Math. Soc. 126 (1998), 1381-1389 Request permission

Abstract:

We prove several distance formulas from a fixed operator in $B(H)$ to some classes of operators connected with the semi-Fredholm ones. Here $H$ is a separable Hilbert space. In particular, Fredholm and upper and lower semi-Fredholm operators have the same boundary in $B(H)$.

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