Mb. Becker, ON INTEGRAL-REPRESENTATION OF THE CONTINUOUS O(N)-POSITIVE DEFINITE FUNCTIONS, Integral equations and operator theory, 31(2), 1998, pp. 133-149
The aim of this paper is to study integral representation for continuo
us O(n)-positive definite functions. Using the Krein method of directi
ng functionals we prove the theorem about integral representation, giv
e the criteria of uniqueness of this representation and description of
all representations in the case of ununiqueness. On the basis of thes
e results we solve analogous problems for continuous radial positive d
efinite functions.