Great point on the chaos! I'm planning to pursue atomic simulation in college, so I've tried to read as much as I can about the field short of the advanced math (hence college, lol). It seems to me that cross cluster synchronization is a massive scaling issue, since you essentially have global state both reduced and broadcasted every couple timesteps.

I've been thinking it would be cool to design chips to be realtime safe—that way there's no need to synctronize—and have further away information delayed (just like relativity) to deal with speed of light communication issues.

Never heard of fleeting interactions, would you mind to elaborate?