operators (we mention the references [1,12,13] where some perturbation of normal operators was dealt with, in a very different context though). So in the present paper we study perturbed normaloperators and the main question asked here is: when is the sum of twonormaloperatorsnormal? We answer this question and we establish the normality of A + B (for normal A and B) in three settings, that is for …
Abstract
The aim of this paper is to give sufficient conditions on two normal operators (bounded or not), defined on a Hilbert space, which make their algebraic sum normal. The results are accompanied by some interesting examples and counter examples.