On second sound at the critical temperature (original) (raw)

Based on low-temperature experimental data in solid dielectric crystals, we derive a model of heat conduction for rigid materials using the theory of thermodynamic internal state variables. The model is intended to admit wavelike propagation of heat below-and diffusive conduction above-a particular temperature value. A rapid decay of the speed of thermal waves occurs just below this temperature, coincident with the conductivity of the material reaching a peak. An analysis of weak and strong discontinuity waves is given in order to exhibit several main features of the proposed model.