Physics Colloquium: Variations on a theme of Aharonov and Bohm revisited
Prof. Michael Berry, Bristol University
The partial anticipation of the Aharonov-Bohm effect (AB) by Ehrenberg and Siday, in terms of interference, was an approximation whose wavefunction was not singlevalued, whose connection with the definitive singlevalued AB wave involves topology: ‘whirling waves’ winding round the flux. The interpretation of AB is a fine illustration of idealization in physics. There are four AB effects, depending on whether the waves and the flux are classical or quantum. In the classical-classical case, many details of the AB wavefunction have been explored experimentally in ripples scattered by a water vortex, where the flow velocity of the water corresponds to the vector potential. In a recent extension, superradiance has been detected. The AB wave possesses a phase singularity, and there is a similar phenomenon in general interferometers. Connections between the AB wave and the Cornu spiral describing edge diffraction led to the prediction of beam deflection (now observed) and to very accurate approximations.
Event Organizer: Prof. Marek Karliner