The Secret Life of the Dipole

The fact that the author of an excellent textbook on electromagnetism could be duped by "hidden momentum" vividly illustrates the problematic nature of its use.

The role of magnetic moments in electrodynamics is examined in this work. The effects are described in the context of conventional quantum electrodynamics expressed in terms of the electromagnetic fields or in the context of an extended Poynting theorem and extended Maxwell equations. These extensions take into account the energetics of interaction of magnetic moments with inhomogeneous magnetic fields. We show how magnetic moment effects are included in either version of ele...

We return to further examination of the need for the existence of magnetic monopoles based on the decades old derivation [Sherman Frankel, Amer. Jour. of Physics, 44, 7, 683-6 1976], of both the monopole-charge force, vec(F) = eg(vec(r) * vec(v)/c)/r^3, as well as the Dirac angular momentum, vec(l_f) = eg hat(r), from P and T conservation alone, without any recourse whatsoever to Maxwell's Equations. The eg product also appeared in the charge conserving equation, deg/dt = 0 =...

The planar quantum dynamics of a neutral particle with a magnetic dipole moment in the presence of electric and magnetic fields is considered. The criteria to establish the planar dynamics reveal that the resulting nonrelativistic Hamiltonian has a simplified expression without making approximations, and some terms have crucial importance for system dynamics.

The classical theory of electrodynamics cannot explain the existence and structure of electric and magnetic dipoles, yet it incorporates such dipoles into its fundamental equations, simply by postulating their existence and properties, just as it postulates the existence and properties of electric charges and currents. Maxwell's macroscopic equations are mathematically exact and self-consistent differential equations that relate the electromagnetic (EM) field to its sources, ...

We study the precession caused by electromagnetic radiation on a magnetic dipole located far from the source. As we show, this entails a net rotation of the dipole in the plane orthogonal to the direction of wave propagation, providing an electromagnetic analogue of gyroscopic gravitational memory. Like its gravitational cousin, the precession rate falls off with the square of the distance to the source, and is related to electric-magnetic duality and optical helicity on the ...

We discuss the algebra and the interpretation of the anomalous Zeeman effect and the spin-orbit coupling within the Dirac theory. Whereas the algebra for the anomalous Zeeman effect is impeccable and therefore in excellent agreement with experiment, the physical interpretation of that algebra uses images that are based on macroscopic intuition but do not correspond to the meaning of this algebra. The interpretation violates the Lorentz symmetry. We give an alternative intuiti...

The Lorentz force of classical electrodynamics, when applied to magnetic materials, gives rise to hidden energy and hidden momentum. Removing the contributions of hidden entities from the Poynting vector, from the electromagnetic momentum density, and from the Lorentz force and torque densities simplifies the equations of the classical theory. In particular, the reduced expression of the electromagnetic force-density becomes very similar (but not identical) to the Einstein-La...

An understanding of the interaction of a point charge and a magnetic moment is crucial for understanding the experiments involving electromagnetic momentum carried by permeable materials as well as the experimentally-observed Aharonov-Bohm and Aharonov-Casher phase shifts. Here we present two simple models for a magnetic moment which have vastly different interactions with a distant point charge. It is suggested that a satisfactory theoretical understanding of the interaction...

The article provides an overview of the behavior and detection of electric and magnetic dipole moments in free atomic and molecular nanoclusters.