Scalar radiation from a point source

Abstract

We consider a classical scalar field, obeying the inhomogeneous Klein-Gordon equation, in the case of a single point source. We propose a definition for the radiated energy-momentum and give an expression for it in terms of the prescribed world line of the source where we assume that the acceleration vanishes outside a finite interval. We find that only the part of the world line with non-vanishing acceleration contributes to the radiation, which travels at all speeds less than but not equal to the speed of light. We briefly discuss the case with more than one point source.