Note on Group Velocity and Energy Propagation

A general proof is given for the equality between group velocity and energy velocity for linear wave propagation in a homogeneous medium with arbitrary spatial and temporal dispersion. In the series of physics \Questions " in the American Journal of Physics, K. M. Awati and T. Howes ask for a general proof of the fact that in linear dispersive wave propagation, energy propagates at the group velocity [1]. Several answers to this question have appeared recently [2], but a general proof has not been provided by any of them. For a stable and nondissipative [3] medium, such a general proof is indeed available from classical, continuum electrodynamics of media [4]. It can be readily argued that this type of proof 1 can be carried out for any other (than electrodynamic) description of a stable, nondissipative, linear (or, more generally, linearized dynamics of a) medium. In an electrodynamic formulation, one chooses to eliminate the \mechanical&quot

Microwave Electronics

Contains a report on a research project.Lincoln Laboratory (Purchase Order DDL-B222)United States Air Force (Contract AF19(604)-5200)United States Navy, Office of Naval Research (Nonr-1841(49)

Spontaneous Radiofrequency Emission from Hot-Electron Plasmas

Contains research objectives.United States Atomic Energy Commission under Contract AT(30-1)-358

Network Synthesis

Contains a report on a research project

Spontaneous Radiofrequency Emission from Hot-Electron Plasmas

Contains report on one research project.U. S. Atomic Energy Commission (Contract AT (30-1)-3581

Microwave Electronics

Contains reports on three research projects

Microwave Electronics

Contains reports on three research projects.United States Department of the NavyLincoln Laboratory (Purchase Order DDL-B222)United States Department of the ArmyOffice of Naval Research (Contract Nonr-1841(49)United States Department of the Air Force (Contract AF19(122)-458

Microwave Electronics

Contains reports on one research project

Microwave Electronics

Contains a report on a research project.United States ArmyUnited States Navy, Office of Naval Research (Contract Nonr-1841(49))Lincoln Laboratory (Purchase Order DDL B-00368)United States Air Force (Contract AF19(604)-7400)United States Nav

Relativistic Beams

Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-030