In this note we characterize all the linear operators on the linear space of n × n complex matrices which preserve the numerical radius and all the linear operators on the real linear space of n × n ...

Linear operators form the cornerstone of analysis in Banach spaces, offering a framework in which one can rigorously study continuity, spectral properties and stability. Banach space theory, with its ...

We prove the following statements about bounded linear operators on a separable, complex Hilbert space: (1) Every normal operator $N$ that is similar to a Hilbert ...

THE modern philosophy of physical science leans strongly to the view, so well expressed by a recent writer, that the concept is synonymous with the corresponding set of operations. The idea of ...