Re: A question about the spin 2 particle.

[brian whatcott <inet@INTELLISYS.NET>]

If one steps past the talk about hypothetical constructs
such as gravitons, there is a paragraph from a Feynman text
at this URL

<http://www.innerx.net/personal/tsmith/Sets2Quarks10.html#sub3>

cited as 'Feynman's Lectures on Gravity, Para 3.4', concerning
two cycles of phase per rotation. The muddiness, such as it is,
is possibly Feynman's then?

Brian


At 11:51 12/25/00 -0600, you wrote:
> Hi all-
>        My complaint is that the whole discussion is muddy, which is why
> Zannelli is getting conflicting answers.  Different people evidently have
> different ideas about what Zennelli is trying to ask.
>        His question appears to be based upon an out-of-context quote of
> language from Adair.  Adair, a fine physicist and talented writer, has
> chosen for reasons of his own to invent the term "DeBroglie amplitude".
> In order to understand the term, and the reason for inventing it, one must
> read Adair, which I (and perhaps many others) have not.  Zannelli
> couples Adair's language with (apparently) a
> recollection, of uncertain accuracy, of something Feynman wrote, which I
> also have not seen.
>        It does seem clear that Zannelli's question has to do with the
> rotation group, which was understood long before the advent of quantum
> mechanics.  It therefore seems that the question, whatever it is, can be
> answered without reference to quantum measurements.  I referred to
> Weinberg, not for a statement of a "position", but for a place to find the
> appropriate mathematical expression along with a brief explanation.
>                                                Regards,
>                                                        Jack
>
> On Sun, 24 Dec 2000, brian whatcott wrote:
>
> > 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!
>
> --
> While [Jane] Austen's majestic use of language is surely diminished in its
> translation to English, it is hoped that the following translation conveys
> at least a sense of her exquisite command of her native tongue.
>                        Greg Nagan from "Sense and Sensibility" in
>                     <The 5-MINUTE ILIAD and Other Classics>
brian whatcott <inet@intellisys.net>  Altus OK
                Eureka!