Perturbation of spectrums of $2\times 2$ operator matrices
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- by Hong Ke Du and Pan Jin PDF
- Proc. Amer. Math. Soc. 121 (1994), 761-766 Request permission
Abstract:
In this paper, we study the perturbation of spectrums of $2 \times 2$ operator matrices such as ${M_C} = \left [ {\begin {array}{*{20}{c}} A & C \\ 0 & B \\ \end {array} } \right ]$ on the Hilbert space $H \oplus K$. For given A and B, we prove that \[ \bigcap \limits _{C \in B(K,H)} {\sigma ({M_C}) = {\sigma _\pi }(A) \cup {\sigma _\delta }(B) \cup \{ \lambda \in C:n(B - \lambda ) \ne d(A - } \lambda )\} ,\] where $\sigma (T),{\sigma _\pi }(T),{\sigma _\delta }(T),n(T)$, and $d(T)$ denote the spectrum of T, approximation point spectrum, defect spectrum, nullity, and deficiency, respectively. Some related results are obtained.References
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Additional Information
- © Copyright 1994 American Mathematical Society
- Journal: Proc. Amer. Math. Soc. 121 (1994), 761-766
- MSC: Primary 47A10; Secondary 47A62
- DOI: https://doi.org/10.1090/S0002-9939-1994-1185266-2
- MathSciNet review: 1185266