Quaternion-valued positive definite functions on locally compact Abelian groups and nuclear spaces.

In this paper we study quaternion-valued positive definite functions on locally compact Abelian groups, real countably Hilbertian nuclear spaces and on the space R N = { ( x 1 , x 2 , … ) : x d ∈ R } endowed with the Tychonoff topology. In particular, we prove a quaternionic version of the Bochner–Minlos theorem. A tool for proving this result is a classical matricial analogue of the Bochner–Minlos theorem, which we believe is new. We will see that in all these various settings the integral representation is with respect to a quaternion-valued measure which has certain symmetry properties. [ABSTRACT FROM AUTHOR]