Saturday, 1 December 2018

quantum mechanics - Lorentz force in Dirac theory and its classical limit


It is well known that in Dirac theory the time derivative of $P_i=p_i+A_i$ operator (where $p_i=∂/∂_i$, $A_i$ - EM field vector potential) is an analogue of the Lorentz force:



$\frac{dP_i}{dt} = e(E_i+[v×B]_i)$


On the other hand, in classical theory we have the same equation for $p_i$ instead of $P_i$. How comes that the effect of $A_i$ in Dirac theory vanishes in the classical limit?




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