3对易规则(commutation rules) M,M,-M,M,=in M. (5.8a M.M.-M.M,=inM, (5.8b) N.N.-N,M.=inM (5.8c) MM-M.M=0 (5.9) 即 [M,M,=hM[M,M,1=0(5.10)3 对易规则(commutation rules)      x y − y x = Mz M M M M i      y z − z y = Mx M M M M i      z x − x z = M y M M M M i 0 2 2 − =     M M z M z M 即    i j = Mk [M ,M ] i 0 2 =   [ , ] M M j (5.8a) (5.8b) (5.8c) (5.9) (5.10)