On accelerated inertial frames in gravity and electromagnetism

When a charged insulating spherical shell is uniformly accelerated, an oppo sitely directed electric field is produced inside. Outside the field is the Born field of a uniformly accelerated charge, modified by a dipole. Radiat ion is produced. When the acceleration is annulled by the nearly uniform gr avity field of an external shell with a 1 + beta cos theta surface distribu tion of mass, the differently viewed Born field is static and joins a stati c field outside the external shell; no radiation is produced. We discuss gr avitational analogues of these phenomena. When a massive spherical shell is accelerated, an untouched test mass inside experiences a uniform gravity f ield and accelerates parallelly to the surrounding shell. In the strong gra vity regime we illustrate these effects using exact conformastatic solution s of the Einstein-Maxwell equations with charged dust. We consider a massiv e charged shell on which the forces due to nearly uniform electrical and gr avitational fields balance. Both fields are reduced inside by the ratio of the g(00) inside the shell to that away from it. The acceleration of a free test particle, relative to a static observer, is reduced correspondingly. We give physical explanations of these effects. (C) 1999 Academic Press.