Some people show interesting classical models of electron spin.
But I don't understood three points yet.
1. Spinor can be expressed as
\begin{pmatrix} \cos \frac{\theta}{2} e^{-i\phi/2} \\<br />
\sin \frac{\theta}{2} e^{+i\phi/2} \end{pmatrix}
So the rotations in
all directions apply to this "two-valued" property.
In the cases of string, when we rotate a thing in several directions at the same time, the string becomes more twisted?
For example, in the hand/book case, when we rotate the right hand + book by 2\pi on the x-y plane, and then rotate it in clockwise or counterclockwise direction by 2\pi on the x-z plane, the right hand becomes more twisted in one case of them?
2. According to the interference experiment, the spinor need to change as e^{i\phi/2}.
Not only after two revolutions, the twisted string or hand can change like this in the process of the rotation?
3. We can define the above \theta and \phi
freely.
(We can define these variables from our observers's viewpoint.)
In this case, the object is still (not moving), and when
we rotate around it by 2\pi, we will see a different thing. By 4\pi rotation, we will see the same thing as the first object.
