Using the Gegenbauer polynomials and the zonal harmonics functions we give some representation formula of the Green function in the annulus. We apply this resul
On Copositive In this paper the author writes a simple characterization for the best copositiveapproximation to elements of C(Q) by elements of finite dimensional
In this paper we study operator valued bases on Hilbert spaces and similar to Schauder bases theory we introduce characterizations of this generalized bases in