2 problems

Let a placement of size $p$ be a finite subset of $\mathds{Z}^n$. For placements $X$ and $Y$, define their centroid by … Define their displacement by … The speed of a trajectory wi…

Let a configuration be a translation-equivalence class of finite placements of pieces on the lattice $\mathds{Z}^n$, and define its speed as the maximum displacement per move among…