orthogonality theorem

Let Γ be a representation for a group of group order h, then sum_R Γ_i (R)_(m n) (Γ_j (R)_(m' n'))^* = h/sqrt(l_i l_j) δ_(i j) δ_(m m') δ_(n n'). The proof is nontrivial and may be found in Eyring et al. (1944).

group | group character | irreducible representation