The spectrum is continuous on the set of quasi-n-hyponormal operators ✩

In this paper it is shown that the spectrum σ, a set-valued function, is continuous when the function is restricted to the set of all ‘quasi-n-hyponormal’ operators acting on an infinite-dimensional separable Hilbert space, where a quasi-n-hyponormal operator is defined to be unitarily equivalent to an n × n upper triangular operator matrix whose diagonal entries are hyponormal operators. © 2006 Elsevier Inc. All rights reserved