Wave propagation with dispersion and damping

We discuss pulse propagation in a dispersive medium with damping. We derive an explicit expression for the center of mass motion and show that when there is damping the center of mass does not travel with constant velocity, as is the case when there is no damping. We also derive an explicit relation connecting pulse propagation in the damped case with that of the undamped case. This allows the transformation from one case to the other. A number of exactly solvable examples are given to illustrate the equations derived.