# Question on tensor notation in group theory

by BWV
Tags: notation, tensor, theory
 P: 328 in the appendix on Group Theory in Zee's book there is a discussion of commutations for SO(3) two questions - does [$J^{ij},J^{lk}] = J^{ij}*J^{lk}-J^{lk}*J^{ij}$? and there is an expression in the appendix that the commutator equals i($\delta^{ik}J^{jl} ...$ i don't understand the why you are multiplying the matrix by the kronecker delta with different upstairs indexes, is not it simply an identity?