Abstract:
The principal series of unitary representations of the Lorentz group is obtained by complexification of the three-dimensional group of rotations and by the solution of the eigenvalue
equation for the Casimir operators. The representation obtained can be expressed simply
in terms of $D$ functions (of the first and second kind) of the group of rotations. The harmonic
analysis of the functions on the group is discussed. Spherical functions on a two-dimensional
complex sphere are constructed.