Theory of heat-pulse propagation in a phonon gas

A theory of the propagation of heat pulses in a phonon system has been constructed. It is based on the solution of the Boltzmann equation for the phonon distribution function in the presence of a heat source and in the relaxation-time approximation. The result obtained is valid at all times, whether longer than, shorter than, or comparable to the mean phonon relaxation time, and provides a basis for quantitative interpretation of the experimental data. © 1968 The American Physical Society.