Lie groups

[ J i j , J k ℓ ] = δ j k J i ℓ − δ j ℓ J i k − δ i k J j ℓ + δ i ℓ J j k {\displaystyle \left[J_{ij},J_{k\ell }\right]=\delta _{jk}J_{i\ell }-\delta _{j\ell }J_{ik}-\delta _{ik...