Title:
Some 0/1 polytopes need exponential size extended formulations

Abstract:
We prove that there are 0/1 polytopes P that do not admit a compact LP formulation. 
More precisely we show that for every n there is a sets X \subseteq {0,1}^n such that conv(X) must have extension complexity at least 2^{n/2 * (1-o(1))}. 
In other words, every polyhedron Q that can be linearly projected on conv(X) must have exponentially many facets. 
In fact, the same result also applies if conv(X) is restricted to be a matroid polytope. 
The paper is available under: http://arxiv.org/abs/1105.0036