Local thermodynamic equilibrium

Summary

Local thermodynamic equilibrium is the assumption that a system out of equilibrium is, near each point, in an equilibrium state. Temperature, pressure and chemical potentials then become fields that vary in space and time. The equilibrium relations, such as the Gibbs relation between entropy and energy, hold at each point. This assumption is the starting point of classical non-equilibrium thermodynamics and of continuum mechanics with heat.