Extended thermodynamics revisited: renormalized flux variables and second sound in rigid solids

Abstract

Propagation of heat waves in rigid bodies is investigated. The originality of the approach is that it rests on a revisited version of extended irreversible thermodynamics. In comparison with earlier developments, two innovations are proposed. First, we depart from the linear approach, best illustrated by Cattaneo's relation, to explore the non-linear regime. Second, the extra variables are no longer the usual dissipative fluxes, but renormalized expressions of the fluxes, in order to include the specific material properties of the systems under study. The present model is particularly well suited for studying heat transport at low temperatures in dielectric crystals.