Appendix A Properties of the Representation Matrices

Now, let (u, v) = Rα(θ, φ′). Here, Rα = Ry(α). We omit the z rotation since that does not affect Yl0 which has no azimuthal dependence. The vector corresponding to coordinates (u, v) is then given by   sinu cos v sinu sin v cos u   =   cosα 0 sinα 0 1 0 − sinα 0 cosα     sin θ′ cosφ′ sin θ′ sinφ′ cos θ′   =   cosα sin θ′ cosφ′ + sinα cos θ′ sin θ′ sinφ′ cosα cos θ′ + sinα sin θ′ (− cosφ′)   . (A.3)