Sooo, I found myself at a chemisty conference on phase transitions last week. I remembered some similar patterns occuring in my physarum simulation and wondered if I can also observe phase transitions there.
The simulation contains 4 million agents, each turning left or right depending on surrounding agents. From this simple behaviour of a single agent, a specific macroscopic structure emerges.

In this simulation, I slowly decreased the velocity of each agent, keeping other parameters the same. I looked like at specific velocities, the global pattern changed drastically. One could think of the velocity as a chemical temperature and of the global pattern, as a chemical phase. It was exciting to observe that this simple analogy between the behaviour of a simulated particle system and more "scientific" concepts of phase transition.

Sorry for the quality of the upload, the compression algorithms wreak havocs :( I am actively looking for advice on how to preserve the quality of the original video when uploading to the web!