Propagation of pulses

The propagation of pulsed wave fields in a homogeneous medium or in a homogeneous line with known dispersion law and damping can be regarded from the ray, wave, and energy points of view. The review describes the most significant theoretical results on one-dimensional pulse propagation, using all three approaches. Greatest attention is paid to the principal part of a high-frequency pulse, the part governed by frequencies closest to the pulse carrier frequency. Paradoxes pertaining to superluminal and negative “group velocities” are resolved, and questions connected with amplification or attenuation of waves in wave beams and active media are discussed.