Gauge Fields, Electromagnetism and the Bohm-Aharonov Effect

Chen Ning Yang

Igor R. Klebanov, Leonard Susskind

Gianfranco Spavieri

Pablo L. Saldanha

The gauge invariance of the Aharonov-Bohm (AB) effect with a quantum treatment for the electromagnetic field is demonstrated. We provide an exact solution for the electromagnetic ground energy due to the interaction of the quantum electromagnetic field with the classical charges and currents that act as sources of the potentials in a classical description, in the Lorenz gauge. Then, we use first-order perturbation theory to compute an extra change on the electromagnetic ground energy due to the presence of a quantum charged particle with known wave function in the system. This energy in general depends on the quantum particle path in an interferometer, which results in an AB phase difference between the paths. The gauge invariance of this AB phase difference is then shown for the magnetic, electric, and the recently proposed electrodynamic versions of the AB effect. However, the AB phase difference could depend on the gauge for nonclosed paths, which reinforces the view that it only can be measured in closed paths.

Alexandre Guay

Xingshu Zhu, Walter C. Henneberger

It is often said that the Aharonov-Bohm (AB) effect (1959) is an effect that is due to the vector potential. This is considered remarkable since a quantity that is not uniquely determined has a measurable effect. The authors show that, in the symmetric Coulomb gauge, (e/c)A(r) is simply the momentum of the electromagnetic field. The effect may equally well be considered an effect of the electromagnetic momentum. Thus, it is possible to discuss the AB effect strictly in terms of observables. The idea that the effect is due to the vector potential is correct, but sheds little light on the physics of the effect.