Chebyshev polynomials and Fourier transform of SU(2) irreducible representation character as spin-tomographic star-product kernel

Abstract

Spin-tomographic symbols of qudit states and spin observables are studied. Spin observables are associated with the functions on a manifold whose points are labelled by spin projections and 2-sphere coordinates. The star-product kernel for such functions is obtained in explicit form and connected with Fourier transform of characters of SU(2) irreducible representation. The kernels are shown to be in close relation to the Chebyshev polynomials. Using specific properties of these polynomials, we establish the recurrence relation between kernels for different spins. Employing the explicit form of the star-product kernel, a sum rule for Clebsch-Gordan and Racah coefficients is derived. Explicit formulas are obtained for the dual tomographic star-product kernel as well as for intertwining kernels which relate spin-tomographic symbols and dual tomographic symbols.