Definition and Relevance of Nonequilibrium Intensive Thermodynamic Parameters

We show that intensive thermodynamic parameters associated to additive conserved quantities can be naturally defined from a statistical approach in far-from-equilibrium steady-state systems, under few assumptions, and without any detailed balance requirement. It may apply, e.g., to dissipative systems such as granular gases where volume or mass is still conserved or to systems with periodic boundary conditions where fluxes of conserved quantities are present. We emphasize the usefulness of this concept to characterize the coexistence of different nonequilibrium phases and discuss the influence of the contact between two different systems, in relation with measurement issues.