In his classic work on radiative transfer, Chandrasekhar introduced the discrete ordinates method for solving the integro-di erential equation of radiative transfer; the spherical harmonics method is a spectral analog of this method. Not surprisingly, there is a close connection between the spherical harmonics and discrete ordinates methods. The spherical harmonics method raises some interestin...

Rotation matrices (or Wigner D functions) are the matrix representations of the rotation operators in the basis of spherical harmonics. They are the key entities in the generation of symmetry-adapted functions by means of projection operators. Although their expression in terms of ordinary (complex) spherical harmonics and Euler rotation angles is well known, an alternative representation using...