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On the Invertibility of the Sum of Operators (1804.07288v4)
Published 19 Apr 2018 in math.FA and math.OA
Abstract: The primary purpose of this paper is to investigate the question of invertibility of the sum of operators. The setting is bounded and unbounded linear operators. Some interesting examples and consequences are given. As an illustrative point, we characterize invertibility for the class of normal operators. Also, we give a very short proof of the self-adjointness of a normal operator when the latter has a real spectrum.