Friday, 8 April 2016

angular momentum - Is there something similar to the Magnus effect for electromagnetism?


Is there something similar to the Magnus effect for electromagnetism? Would a spinning particle generate a centripetal force moving through something like a circular accelerator? And how would you calculate this?




Answer



Electron spin contributes to the centrifugal force on an electron.


Compare the wave function of the hydrogen atom for the Klein-Gordon and the Dirac equation. The KG energy values are


$E_{nl} = \frac{m}{\sqrt{1+[\alpha^2/(n-\delta_l)^2]}}$


with $\delta_l=l+\frac{1}{2}$. The Dirac eigenvalues are obtained by replacing $l\rightarrow j\pm \frac{1}{2}$. See QFT, Itzykson&Zuber, Ch. 2.3.


The reason is that the radial equation in these cases contains the centrifugal potential $\frac{L^2-\alpha^2}{r^2}$ (KG) and $\frac{J^2\alpha^2}{r^2}$ (Dirac). This clearly proves that electron spin like orbital angular momentum exhibits a centrifugal force.


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