Hi! Thanks for pay attention. I am learning spinfoam model through Rovelli's book and other reviews. I don't know how to perform the derivation of the integration:
\int{dU R^{j1}(U)^{a}_{a'} R^{j2}(U)^{b}_{b'} R^{j3}(U)^{c}_{c'}=v^{abc}v_{a'b'c'}}
the integration is over SU(2), the...