Geometric proofs for convex hull defining formulations

A conjecture appeared recently in Cacchiani et al. (2013) that a proposed LP relaxation of a certain integer programming problem defines the convex hull of its integer points. We review a little known technique described in Zuckerberg (2004) that can be used to construct geometric proofs that an LP relaxation is convex hull defining. In line with this technique, we show that their conjecture is correct.