The Aharonov-Bohm effect (AB) concerns the role in quantum physics of the magnetic vector potential of an impenetrable line of magnetic flux. Its partial anticipation by Ehrenberg and Siday, in terms of interference, was an approximation whose wavefunction was not singlevalued, and whose connection with the singlevalued AB wave involves topology: ‘whirling waves’ winding round the flux. 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. The AB wave possesses a phase singularity, and there is a similar phenomenon in general interferometers. Gauge-invariant AB streamlines exhibit extraordinary sub-wavelength structure. Connections between the AB wave and the Cornu spiral describing edge diffraction lead to extremely accurate approximations.
Professor Sir Michael Berry (University of Bristol) is known as an author of more than 500 scientific articles. His outstanding research has been devoted to various topics in quantum mechanics and optics. Specializing in semiclassical description of the related effects, Prof. Berry made a substantial contribution to revealing some fundamental aspects of these scientific fields. Especially, he is famous for the elucidating the phenomenon of the geometric phase as a general property of quantum and optical systems.
Michael Berry received his undergraduate degree (with honors) from Exeter University in 1962. Then, he did his postgraduate research at St. Andrews University (1962-1965), leaving with Ph.D. degree in theoretical physics. Since 1965, he has been at Bristol University, first as a postdoctoral fellow, then as a Lecturer (1967-1974) and Reader (1974-1979). In 1979 he became a Professor of Physics and thereafter a Royal Society Research Professor (1988-2006). Currently, Sir Berry is a Melville Wills Professor (Emeritus) of Physics at Bristol University.