Proceedings of the American Mathematical Society

Author(s): Haïkel Skhiri
Journal: Proc. Amer. Math. Soc. 126 (1998), 1381-1389.
MSC (1991): Primary 47A53; Secondary 47A55
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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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