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Spin and direction of motion

  1. Aug 15, 2010 #1
    How this two are related? I read somewhere that the spin is always parallel to the direction of motion of particle. If the direction of motion changes by some magnetic field (Lorentz force) what happens to tha spin? Will its axis direction change too?
     
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  3. Aug 15, 2010 #2

    Fredrik

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    That's true for massless particles, but not for massive particles.
     
  4. Aug 15, 2010 #3
    Why it's true for massless particles? Is there any explanation to this?
    Btw thnx for your answer!
     
  5. Aug 15, 2010 #4

    Fredrik

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    There is, but it's very complicated. It's a part of the mathematical theory of massless representations of the Poincaré group. If you're a bit of a masochist, check out section 2.5 in Weinberg's "The quantum theory of fields" (vol. 1).
     
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