Energy Velocity, Damping, and Elementary Inversion

摘要

Our numerical computation of precursors shows that damping increases the speed offrequency components to a degree that is consistent with energy velocity. The speedup here is slight, and a medium that has been called highly absorptive exhibits no speedup. These small effects lead us to question the extent to which energy velocity would be more useful than group velocity in the laboratory. We also introduce an especially simple method for measuring permittivity. The method is useful when damping affects wave speed no more than slightly, as happens in all the numerical simulations cited or reported here.