2-levelness of Marked Poset Polytopes and the Ehrhart polynomial

Abstract

It is already known that order polytopes and chain polytopes are always 2-level polytopes. In general, this is not true for marked order and marked chain polytopes. We study the geometry of marked order polytopes, marked chain polytopes, and marked chain-order polytopes, providing a comprehensive characterisation of 2-levelness for these polytopes. Furthermore, we present an exact formula for the Ehrhart polynomial of marked order polytopes. Because of their connection to marked chain and marked chain-order polytopes, this polynomial is also the Ehrhart polynomial of these polytopes.