Talks

In this article we compare the set of integer points in the homothetic copy ${n\Pi}$ of a lattice polytope ${\Pi\subseteq{{\mathbb R}}^d}$ with the set of all sums${ x_1+\ldots +xn}$ with ${x_1,\ldots,x_n\in \Pi\cap{{\mathbb Z}}^d}$ and ${n\in{{\mathbb N}}}$. We give conditions on the polytope ${\Pi}$ under which these two sets coincide and we discuss two notions of boundary for subsets of${{{\mathbb Z}}^d}$ or, more generally, subsets of a finitely generated discrete group.