0 0.5 1 1.5 2 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 0.2 0.4 0.6 0.8 1 0 0.5 1 1.5 2 0 0.01 0.02 0.03 0.04 0.05 0.06 J 0 0.4 0.8 1.2 1.6 0.01 0.02 0.03 0.04 0.05 0.06 J FIG. 7: Upper panels: bulk density for (a) fixed α and (b) fixed β . Lower panels: current for (c) fixed α and (d) fixed β . System size L = 200. A. Phase diagram Of principal interest in determining the phase diagram are the bulk density and the current as functions of the rates α and β . These results are summarized in Fig. 7, showing evidence of both continuous and discontinuous phase transitions, depending on the rates. We see that for low α ( α < 0 . 8 or so) and β < α the system is in the high-density phase, in which density and current depend only on β , whereas for β > α , and β < 0 . 6 or so, the system is in the low-density phase in which density 14 (d) (c) (a) (b)