Fluctuation–dissipation equation of asymmetric simple exclusion processes

Summary. We consider asymmetric simple exclusion processes on the lattice Zopf; d in dimension d ≥3. We denote by L the generator of the process, ∇ the lattice gradient, η the configuration, and w the current of the dynamics associated to the conserved quantity. We prove that the fluctuation–dissipation equation w = Lu + D ∇η has a solution for some function u and some constant D identified to be the diffusion coefficient. Intuitively, Lu represents rapid fluctuation and this equation describes a decomposition of the current into fluctuation and gradient of the density field, representing the dissipation. Using this result, we proved rigorously that the Green-Kubo formula converges and it can be identified as the diffusion coefficient.