Abstract:
A basis of eigen-vectors of the generator producing the Wigner $d$-functions is constructed
in the space of irreducible unitary representation of the $U(3)$-group. Eigenvectors
of the generator are described in terms of a certain class of orthogonal polynomials
in two discrete variables which are generalizations of the Kravchuk polynomials.
Continuous analogues of these polynomials are studied. Decomposition of the
$d$-functions into exponential functions is obtained.