Phase diagram and edge effects in the ASEP with bottlenecks

We investigate the totally asymmetrical simple exclusion process (TASEP) in the presence of a bottleneck, i.e. a sequence of consecutive defect sites with reduced hopping rate. The influence of such a bottleneck on the phase diagram is studied by computer simulations and a novel analytical approach. We find a clear dependence of the current and the properties of the phase diagram not only on the length of the bottleneck, but also on its position. For bottlenecks near the boundaries, this motivates the concept of effective boundary rates. Furthermore the inclusion of a second, smaller bottleneck far from the first one has no influence on the transport capacity. These results will form the basis of an effective description of the disordered TASEP and are relevant for the modelling of protein synthesis or intracellular transport systems where the motion of molecular motors is hindered by immobile blocking molecules.