sci.physics.particle

On 24 Aug., 15:00, Ben Rudiak-Gould wrote:
> john_m_stan...@ wrote:
> > (A) In quantum theory, angular momentum is a
> > multiple of hbar/2. This statement is valid
> > without restrictions.
>
> > (B) On the other hand, for large bodies it is said
> > that there is an uncertainty relation between
> > angular momentum and phase:
> > Delta J Delta phi > hbar/2
>
> > How can both (A) and (B) be correct? Why does the
> > quantization of angular momentum not apply
> > to macroscopic bodies?
>
> For angular motion the eigenbasis of states is discrete, but that doesn't
> mean you can't have an object in a superposition of eigenstates. You can
> still combine eigenstates to get a wave packet that looks like a Gaussian
> distribution in both the (angular) position and (angular) momentum bases,
> with the widths of the distributions constrained by an uncertainty relation.

Ok, that is a good point!

>
> Also, quantization of angular momentum doesn't apply in any case to
> macroscopic (thermodynamic) objects, because they leak information to their
> environment. To get quantization you need path interference, and to get path
> interference you need a thermodynamically closed system.

Juast to undedrstand the argument: why does one need path interference
for angular momentum quantization? I have never heard that.

John


> -- Ben