Engineering Physics Annotation << Back GROUP VELOCITY AND ENERGY TRANSPORT VELOCITY IN DISSIPATIVE MEDIA M.A. MIKAELYAN For the wave process with an arbitrary dispersion law ω = ω'(k) +iω''(k) a rigorous defi nition of the group velocity vg is suggested. For a monochromatic approach the ultimate expression vg(k) is received. The condition under which vg(k) takes the Kuzelev- Rukhadze form is obtained. In the general case it turns out that vg(k) is determined not only by the dispersion law ω(k), but also by other elements of the initial problem. The models of some dissipative media (non-polar and polar dielectrics, plasma, metal) are considered; for these media explicit expressions for the fi eld energy density are obtained. With reference to the above dissipative media it is shown that vg(k) determines the fi eld energy transport velocity that does not exceed the velocity of light in vacuum. Expressions for the energy transport velocity were also obtained for the case when the dispersion law is given in the form k=k'(ω)+ik''(ω) that corresponds to the boundary problem. Particular attention is paid to the notion of a complete set of values, knowledge of which allows determining their evolution without recourse to prehistory. It is these values that defi ne the state of the system; the energy is a function of state (not prehistory). Key words: group velocity, energy transport velocity, dissipative medium, fi eld energy, initial value problem. Contacts: E-mail: mikhail@bk.ru Pp. 18-29.