Pseudo-Character Expansions for U(N)-Invariant Spin Models on CP^{N-1}
  We define a set of orthogonal functions on the complex projective space CP^{N-1}, and compute their Clebsch-Gordan coefficients as well as a large class of 6-j symbols. We also provide all the needed formulae for the generation of high-temperature expansions for U(N)-invariant spin models defined on CP^{N-1}. 
Attilio Cucchieri, Tereza Mendes and Andrea Pelissetto