EXTENDED IRREVERSIBLE THERMODYNAMICS AND NON-EQUILIBRIUM TEMPERATURE

ABSTRACT. We briefly review the concept of non-equilibrium temperature from the per-spectives of extended irreversible thermodynamics, fluctuation theory, and statistical me-chanics. The relations between different proposals are explicitly examined in two espe-cially simple systems: an ideal gas in steady shear flow and a forced harmonic oscillator in a thermal bath. We examine with special detail temperatures related to the average molec-ular kinetic energy along different spatial directions, to the average configurational energy, to the derivative of the entropy with respect to internal energy, to fluctuation-dissipation relation and discuss their measurement. 1