A matricial analogue of Fejer's theory for different types of convergence

We describe the space of operators on a Hilbert space with the summable Fourier expansion and prove that this space does not depend on the kind of summability method. We consider the same problem in the spaces of operators with respect to unitarily invariant norms. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)