Commutator Relation

  • #1

Homework Statement



To show [J2, J+] = 0

2. Homework Equations


J+ = Jx + i Jy

[J2, Jx ] = 0

[J2, Jy ] = 0


The Attempt at a Solution



Step 1: L.H.S. = [J2, J+]

Step 2: L.H.S. = [J2, Jx + i Jy ]

Step 3: L.H.S. = [J2, Jx ] + i [J2, Jy ]

Step 4: L.H.S. = 0 + 0

Step 5: L.H.S. = 0

L.H.S. = R.H.S.

I'm kinda confuse about 'Step 3'. Can we take out the 'i' from whole bracket? If yes, then do I have to give any reason for it?
 

Answers and Replies

  • #2
71
5
Go ahead and write out the full commutator in step 2. What do you get?
 

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