Essential approximate point spectra and Weyl's theorem for operator matrices |
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| Authors: | Xiaohong Cao Bin Meng |
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| Affiliation: | College of Mathematics and Information Science, Shaanxi Normal University, Xi'an 710062, People's Republic of China |
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| Abstract: | ![]()
When A∈B(H) and B∈B(K) are given, we denote by MC the operator acting on the infinite dimensional separable Hilbert space H⊕K of the form  . In this paper, it is shown that a 2×2 operator matrix MC is upper semi-Fredholm and ind(MC)?0 for some C∈B(K,H) if and only if A is upper semi-Fredholm and |
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| Keywords: | Weyl's theorem a-Weyl's theorem Essential approximate point spectrum |
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