Energy velocity for hyperbolic dispersive waves

Abstract

In this note the concept of energy velocity for linear dispersive waves is discussed in the uniaxial case. When energy is not conserved, the identification of energy velocity with the kinematic concept of group velocity is not valid as shown in some examples of physical interest. For dispersive waves of hyperbolic type a general expression for energy velocity is deduced, which yields the group velocity only for conservative waves. In special cases of nonconservative waves the energy velocity is shown to equal the phase velocity. Examples are also presented.