Spin-weighted spherical harmonics
Relation to Wigner rotation matrices
Relation to Wigner rotation matrices
------------------------------------

D^l\_{\-m s}(\\phi,\\theta,\-\\psi) \=\\left(\-1\\right)^m \\sqrt\\frac{4\\pi}{2l\+1} {}\_sY\_{l m}(\\theta,\\phi) e^{is\\psi}
This relation allows the spin harmonics to be calculated using recursion relations for the [\-matrices](/wiki/Wigner_D-matrix "Wigner D-matrix").


What is the role of the square root term in the formula for spin harmonics?