Abstract
This paper continues an earlier study of those bounded operators on a Hilbert space at which the spectrum is continuous, where the spectrum is considered as a function whose domain is the set of all bounded operators furnished with the norm topology and whose range is the collection of compact subsets of the complex plane furnished with the Hausdorff metric. In this paper the points of continuity of the essential spectrum, the approximate point spectrum, and certain related subsets of the spectrum are characterized.
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The first author was supported by National Science Foundation Grant MCS 77-28396.
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Conway, J.B., Morrel, B.B. Operators that are points of spectral continuity, II. Integr equ oper theory 4, 459–503 (1981). https://doi.org/10.1007/BF01686497
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DOI: https://doi.org/10.1007/BF01686497