Relativistic Dynamics of a Charged Sphere : Updating the Lorentz-Abraham Model

This is a remarkable book. Arthur Yaghjian is by training and profession an electrical engineer; but he has a deep interest in fundamental questions usually reserved for physicists. Working largely in isolation he has studied the relevant papers of an enormous literature accumulated over a century. The result is a fresh and novel approach to old problems and to their solution. Physicists since Lorentz have looked at the problem of the equations of motion of a charged object primarily as a problem for the description of a fundamental particle, typically an electron. Yaghjian considers a mac- scopic object, a spherical insulator with a surface charge. was therefore not tempted to take the point limit, and he thus avoided the pitfalls that have misguided research in this field since Dirac's famous paper of 1938. Perhaps the author's greatest achievement was the discovery that one does not need to invoke quantum mechanics and the correspondence pr- ciple in order to exclude the unphysical solutions (runaway and pre-acc- eration solutions). Rather, as he discovered, the derivation of the classical equations of motion from the Maxwell-Lorentz equations is invalid when the time rate of change of the dynamical variables too large (even in the relativistic case). Therefore, solutions that show such behavior are inc- sistent consequences. The classical theory thus shown to be physically consistent by itself. It embarrassing--to say the least--that this obs- vation had not been made before.