Ehrhart -vectors of hypersimplices
arXiv:1104.5292
Abstract
We consider the Ehrhart -vector for the hypersimplex. It is well-known that the sum of the is the normalized volume which equals an Eulerian numbers. The main result is a proof of a conjecture by R. Stanley which gives an interpretation of the coefficients in terms of descents and excedances. Our proof is geometric using a careful book-keeping of a shelling of a unimodular triangulation. We generalize this result to other closely related polytopes.