In this paper we study strictly positive definite functions on the unit sphere of the m-dimensional Euclidean space. Such functions can be used for solving a scattered data interpolation problem on spheres. Since positive definite functions on the sphere were already characterized by Schoenberg some fifty years ago, the issue here is to determine what kind of positive definite functions are act...

Strictly positive definite functions are used as basis functions for approximation methods in various contexts. Using a group theoretic interpretation of Bochner’s Theorem we give a sufficient condition for strictly positive definite functions on a semi-direct product which are invariant under the natural action of a given subgroup. As an application strictly positive definite, reflection invar...

Concepts of abstract harmonic analysis can be used to provide a unifying framework for basis function methods, like radial basis functions in Euclidean spaces or zonal basis functions on the sphere. To illustrate how these concepts can be applied reflection invariant functions are considered. A specialization of the BochnerGodement Theorem leads to a characterization of suitable basis functions. §

In this paper we present an overview of the implications of our previously derived results for positive definite kernels on the general theory of positive definite functions. We begin by exploring the consequences of a set of differential inequalities on the global behaviour of a smooth positive definite function of one real variable. Then we propose a natural extension of this study to the com...

We establish the positive definiteness of some functions and of some matrices that arise as solutions of generalized Lyapunov equations. Mathematics Subject Classification (2000) : 42A82, 47A62, 15A24, 15A48.

is always non-negative, for any positive integer n and all points x1, . . . , xn in H is said to be positive definite on Hilbert space. In Schoenberg (1938), it was shown that a function is positive definite on Hilbert space if and only if it is completely monotonic, and this characterization is of central importance in the theory of radial basis functions and learning theory. In this paper, we...