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**UNC-CH Physics and Astronomy Colloquium**

Norman Margolus, Massachusetts Institute of Technology

**“Counting distinct states in physical dynamics”**

Since counting distinct states is so fundamental in statistical mechanics, why isn’t it a basic quantity in all of physics? It turns out that, in fact, it is. Like entropy, energy is also a maximum count of distinct states—in time. In this talk I review how finite average energy makes distinct-state finite, despite space and time being treated as continuous. I discuss the relationship between maximum distinctness, discreteness and uncertainty. And I show that classical lattice gas models are foundational for dynamics, in the same way that they are in statistical mechanics.