Posts Tagged ‘Aharonov

Ghostly Influence of Distant Magnetic Field

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Electrons passing around opposite sides of an electromagnet feel negligible magnetic fields (purple), but the electromagnetic potential (green circles and arrows) affects them in opposite ways, leading to measurable consequences. Before the effect was proposed in 1959, physicists thought fields must interact directly with particles to cause measurable electromagnetic effects.

A 1959 Physical Review paper claimed that an electric or magnetic field could influence quantum particles even though the particles never experienced the field directly. In classical electromagnetism there is no other way to influence a particle besides direct contact with the fields. Even though quantum mechanics was well-established by then, the idea met with widespread skepticism. Arguments over the theoretical analysis and attempts at experimental verification continued for some years, but eventually the so-called Aharonov-Bohm effect took its place as a legitimate demonstration of unexpected physics in the quantum world.

In classical electromagnetism, electric and magnetic fields are the fundamental entities responsible for all physical effects. There is a compact formulation of electromagnetism that expresses the fields in terms of another quantity known as the electromagnetic potential, which can have a value everywhere in space. The fields are easily derived theoretically from the potential, but the potential itself was taken to be purely a mathematical device, with no physical meaning….. Read the rest of this entry »

Written by physicsgg

July 25, 2011 at 10:36 pm


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