Figure 3-9 shows the basic interactions
Figure 3-9: The
basic long-range interactions acting in the direction of 
. Particles at sites R lattice units apart
are flipped from the solid link
directions to the dashed directions provided there is initially a
particle in both the solid links and no particles in either of the
dashed links.
acting along the
direction on two sites a distance R
apart. The interaction can take place only if there are particles
travelling in both the directions indicated by the solid arrows and if
there are no particles travelling in the direction of either of the
dashed arrows. If this is the case the particles are flipped from the
solid link to the dashed link. These five basic interactions are also
applied along the 
and 
directions.