It is well known that the electric and magnetic Aharonov–Bohm effects may be formally described on an equal footing using the four-vector potential in a relativistic framework. We give an illustrative manifestation of both effects in a single configuration in which the path of the charged particle determines the weight of the acquired electric and magnetic relative phases. The phases can be distinctively obtained in the Coulomb gauge. The examples illustrate that, although each of the relative phases is gauge dependent, their sum is gauge invariant.

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2.
The same effect can be obtained by choosing a smooth non-singular vector potential A(x,t) that is confined in both space and time. Outside the confined region the potential vanishes. Within a certain part of the confined region, it is constant. In the intermediate area it smoothly decays from a constant value to zero. It is only in this region that the electric and magnetic fields do not vanish. Such a potential imposes charge and current densities different from Eqs. (5) and (6), but the setup is still non-radiating. The same combined electric and magnetic Aharonov–Bohm effects are obtained if the two interfering wave packets do not enter (in space-time) the intermediate regions, where E and B are non-trivial. We have used the delta (and step) function(s) to simplify the calculations, specifically those of the charge and current densities.
3.
When treating the sources quantum mechanically, the Coulomb gauge is essential because it describes the back reaction correctly. See
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