2. A-field (actually, A-potential):

A very loose, nearly slang term for the vector magnetic potential. The A-potential is a dynamic potential and is a real entity since it produces observable effects. It is not a mathematical convenience as was originally thought. This is detailed in the second volume of Feynman's three volumes of physics. The curl of the A-potential is considered to produce a magnetic B-field. Indeed, it turned out that the B-field may be separated from the magnetic field, as the experiment reported by Feynman details. When separated, it is often referred to as the "curl-free vector potential." The Aharonov-Bohm effect, of increasing importance in physics, proves the existence of the independent curl-free vector potential and its ability to produce observable results.