Distributed fixed resources exchanging particles: Phases of an asymmetric exclusion process connected to two reservoirs

We propose and study a conceptual one-dimensional model to explore how the combined interplay between fixed resources with unlimited carrying capacity and particle exchanges between different parts of an extended system can affect the stationary densities in a current-carrying channel connecting different parts of the system. Our model is composed of a totally asymmetric simple exclusion process (TASEP) connecting two particle reservoirs without any internal dynamics, but which can directly exchange particles between each other, ensuring nonvanishing currents in the TASEP lane in the steady states. The total particle number in the system that defines the "resources" available, although held conserved by the model dynamics, can take any value giving unrestricted carrying capacity. We show how the resulting phase diagrams of the model are controlled by relevant parameters, together with the total available resources. These control parameters can be tuned to make the density on the TASEP lane globally uniform or piecewise continuous with localized domain walls, and can also control populations of the two reservoirs. In general, the phase diagrams are quite different from a TASEP with open boundaries. However, in the limit of a large amount of resources, the phase diagrams in the plane of the control parameters become topologically identical to that for an open TASEP along with delocalization of domain walls.