The Time-Domain Theory of Forerunners

The time-domain theory of forerunners (precursors) in temporally dispersive, nonmagnetic, isotropic materials is developed using the propagator technique. Specifically, the impulse response at a (comparatively) large propagation depth is expanded in two different ways: (a) with respect to the wave-front and (b) with respect to slowly varying field components. A few numerical examples illustrating the theory are given