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Mar6-12, 06:46 PM
P: 755
Quote Quote by lugita15 View Post
That's actually not true. If you construct Hilbert space operators out of the representation theory of the Galilei group, just as you do the analogous thing with the Poincare group in QFT, you will naturally get spin angular momentum; see Ballentine for details. What is genuinely relativistic is the spin-statistics theorem.
Which section in Ballentine do you have in mind? Substituting QxP by QxP+S (as he does in chapter 3) seems pretty ad hoc to me.

For relativistic QM, there are physical reasons for the existence of spin. I really wonder what such reasons could be in the non-relativistic case.