Self-organization, phase transitions, and caveats from simulation
Raissa D'Souza, Microsoft Research, Microsoft Corporation, Redmond, Washington
The Biham-Middleton-Levine traffic model is perhaps the simplest system
exhibiting phase transitions and self-organization. It is a computer model of
"traffic" moving on a lattice, which shows a sharp phase transition from free
flowing to fully jammed as a function of the initial density of cars. Though
studied extensively, we find new intermediate structures that contradict the
existence of a simple phase transition. The structures have a crisp geometric
order and can be exactly periodic, but most importantly show extreme sensitivity
to the underlying lattice width to length aspect ratio. A key to uncovering the
novel behavior was visualizing the kinetic pathway along which the system
self-organizes.
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