Figure 3

Model figure. (a) Two dimensional square lattice with occupied (n = 1) or unoccupied (n = 0) sites. Filled circles indicate the occupied sites. Inclinations of the rods towards the horizontal direction show respective particle orientations θ ∈ [0,π]. (b) Equilibrium move: particle can move to any of the four neighbouring sites with equal probability 1/4. (c,d) Active move: particle can move to either of its two neighbouring sites with probability 1/2, if unoccupied, in the direction it is more inclined to, i.e., along BD in (c), and AC in (d).