on utilizing the spectral representation of selfadjoint operators in hilbert spaces, some error bounds in approximating $n$-time differentiable functions of selfadjoint operators in hilbert spaces via a taylor's type expansion are given.

In this article, we use two concepts, measure of non-compactness and Meir-Keeler condensing operators. The measure of non-compactness has been applied for existence of solution nonlinear integral equations, ordinary differential equations and system of differential equations in the case of finite and infinite dimensions by some authors. Also Meir-Keeler condensing operators are shown in some pa...

g-frames in hilbert spaces are a redundant set of operators which yield a repre-sentation for each vector in the space. in this paper we investigate the connection betweeng-frames, g-orthonormal bases and g-riesz bases. we show that a family of bounded opera-tors is a g-bessel sequences if and only if the gram matrix associated to its denes a boundedoperator.

Let G and $$\Omega $$ be two planar domains. We give necessary sufficient conditions on a sequence $$(\phi _n)$$ of eventually injective holomorphic mappings from to for the existence function $$f\in H(\Omega )$$ whose orbit under composition by is dense in H(G). This extends result same nature obtained Grosse-Erdmann Mortini when $$G=\Omega . An interconnexion between topological properties ap...