Spherical harmonics for the compactification of IIB supergravity on S_5

Abstract

We give a detailed derivation of the spherical harmonics which correspond to the spectrum in the tables of the 1985 paper by Kim, Romans and the author on the Kaluza-Klein dimensional reduction of IIB supergravity on $S_5$ to 5-dimensional maximal anti de Sitter supergravity. We show how all methods that have been used in the literature to obtain spectra if the internal space is $S_n$ can be derived from embedding $S_n$ in $R^{n+1}$. A crucial observation for spin 1/2 spherical harmonics is that one also needs a local Lorentz rotation if one transforms to polar or stereographic coordinates. The relation to the vector spherical harmonics of electromagnetism is also worked out.