Let X and Y be Banach (or quasi-Banach) spaces and let T ∈ L(X,Y ) be a compact operator. In order to measure “the degree of compactness of T” one can use the asymptotic decay of the sequence of… (More)

We provide a simple algorithm that constructs an exact minimizer for the E-functional E(t, f ; L, BV ) = inf ‖g‖L∞≤t ‖ f − g‖BV . Here L, BV stand for the space of bounded functions and the space of… (More)

We show that if the duality between a Banach space A and its anti-dual A* is given by the inner product of a Hilbert space H, then (A, A*)1/2,2 = H = (A,A*)[l,2~, provided A satisfies certain mild… (More)

We establish interpolation formulæ for operator spaces that are components of a given quasi-normed operator ideal. Sometimes we assume that one of the couples involved is quasi-linearizable, some… (More)

Acknowledgements I would like to express my deepest gratitude to my supervisors Professor Hans Triebel and Professor Hans-Jürgen Schmeisser for many fruitful discussions, suggestions and remarks. I… (More)

We investigate dual spaces of interpolation spaces defined by means of polygons. We first show that dual spaces may fail to be intermediate spaces with respect to the dual Ar-tuple, and then we prove… (More)