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Re: A question about the spin 2 particle.



Robert Zannelli appears to be comprising Feynman's explanation that there are
two cycles of a spin two particle's state in 360 degrees of rotation.
This does not appear to contradict Weinberg's position that a one particle
integer spin state is invariant in 360 degrees of rotation (at least, to
an innocent bystander).



At 18:11 12/22/00 -0600, you wrote:
Hi all-
This is unnecessarily complicated and confusing. The answer is
that a 1-particle bosonic (integer spin) state is invariant under a
360 degree rotation. A 1-particle fermionic state changes sign under such
a rotation.
End of story. For more detail see Weinberg, Vol. I, p. 89, where
you will see that the result is not quantum-mechanical but has to do
with representations of the Poincare' group.
Regards,
Jack



On Fri, 22 Dec 2000, Robert B Zannelli wrote:

OK Let me see if I get this. The number of a particles' eigenstates is
given
by the equation n=2s+1. Any particle will be not be in any defined state
until a measurement is made of that particles spin. An unmeasured particle
will be in a superposition of all it's possible eigenstates. For a spin 2
particle there are 5 possible states which are-2,-1,0,1,2 . Now if we take
the vector in the Hilbert space which defines the mix of these states
and our
2 spin particle superposition states consist of only amplitudes in even
number states then a 180 degree rotation will be a complete cycle. Should
there be any probability amplitude for any odd numbered state we would
need a
360 degree rotation to complete a full cycle. In any case a 360 degree
rotation always returns the same amplitude.

brian whatcott <inet@intellisys.net> Altus OK
Eureka!