A relationship of mean-field theory for a driven lattice gas to an exact equilibrium density functional

We consider the totally asymmetric exclusion process (TASEP) of particles on a one-dimensional lattice that interact with site exclusion and are driven into one direction only. The mean-field approximation of the dynamical equation for the one-particle density of this model is shown to be equivalent to the exact Euler–Lagrange equations for the equilibrium density profiles of a binary mixture. In this mixture particles occupy one (two) lattice sites and correspond to resting (moving) particles in the TASEP. Despite the strict absence of bulk phase transitions in the equilibrium mixture, the influence of density-dependent external potentials is shown to induce abrupt changes in the one-body density that are equivalent to the exact out-of-equilibrium phase transitions between steady states in the TASEP with open boundaries.