engleski

Phase transitions in driven diffusive systems far from equilibrium

Nonequilibrium phase transitions are studied in several proposed generalizations of the asym- metric simple exclusion process (ASEP). ASEP is a simple model belonging to the class of so-called driven diffusive systems maintained far from equilibrium by external field and nonequi- librium boundary conditions. We propose a generalization of ASEP that replaces short-range with long-range hopping, where hopping length l is taken from the probability distribution that follows a power law p_l ∝ l^−(1+σ) with σ > 1. Although the resulting phase diagram re- mains the same, we observe changes both at the first- and the second-order transition lines for 1 < σ < 2, while the short-range limit sets in for σ > 2. Using the same model we also address the long-standing question of whether a “slow” site in ASEP always induces phase separation. By including a “slow” site in the long-range model we show that the transition to the non-separated phase is possible and we find the exact transition point. In the case of finite concentration of defects (i.e. disorder), we show that contrary to the one-dimensional case where disorder always induces phase separation, in the two-dimensional ASEP a regime exists in which phase separation is absent.

driven diffusive systems; nonequilibrium steady states; phase diagrams; defects; disordered systems

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