  The nonloclal exchange of the conserved, gauge invariant quantity
$e^{\frac{i}{\hbar} (p_{k}-\frac{e}{c}A_{k})L^{k}}, L^{k}=const., k=1,2$
between the charged particle and the magnetic flux line (in the $k=3$
direction), is responsible for the Aharonov-Bohm effect. This exchange occurs
at a definite time, before the wavepackets are brought together to interfere,
and can be verified experimentally.
