Abstract Let A be an n × n Hermitian matrix and A = UΛUH be its spectral decomposition, where U is a unitary matrix of order n and Λ is a diagonal matrix. In this note we present the perturbation ...

We prove that each element of the open unit ball of a C*-algebra 𝔄 is the mean of a finite number of unitary elements of 𝔄 – the closer to the surface, the more unitaries are needed in general. Each ...