This paper is concerned with asymptotic formulae for sequences of positive linear operators acting on weighted spaces of continuous functions defined on a real interval. The main result provides a characterization of those continuous functions for which a pointwise asymptotic formula holds true. The method is essentially based on a characterization of the domains of generators of C0-semigroups in terms of asymptotic formulae. Finally, several applications concerning, among others, Kantorovich operators, exponential operators, Gauss-Weierstrass operators and

In this paper we study a class of elliptic second-order differential operators on finite dimensional convex compact sets whose principal part degenerates on a subset of the boundary of the domain. We show that the closures of these operators generate Feller semigroups. Moreover, we approximate these semigroups by iterates of suitable positive linear operators which we also introduce and study in this paper for the first time, and which we refer to as modified Bernstein-Schnabl operators. As a consequence of this approximation we investigate some regularity properties preserved by the semigroup. Finally, we consider the special case of the finite dimensional simplex and the well-known Wright-Fisher diffusion model of gene frequency used in population genetics.

In questo lavoro si propone una caratterizzazione della risolubilità di un problema differenziale associato all'equazione di~Black-Scholes-Merton che utilizza alcune tecniche della teoria dei semigruppi. A tal riguardo, una piccola sezione preliminare fornisce dei richiami utili ad illustrare un'interconnessione fra la teoria degli operatori e quella delle equazioni alle derivate parziali.