Many 2-level polytopes from matroids

Abstract

The family of 2-level matroids, that is, matroids whose base polytope is 2-level, has been recently studied and characterized by means of combinatorial properties. 2-level matroids generalize series-parallel graphs, which have been already successfully analyzed from the enumerative perspective. We bring to light some structural properties of 2-level matroids and exploit them for enumerative purposes. Moreover, the counting results are used to show that the number of combinatorially non-equivalent (n-1)-dimensional 2-level polytopes is bounded from below by $c\cdot n^{-5/2}\cdot {\rho }^{-n}$, where $c\approx 0.03791727$ and ${\rho }^{-1}\approx 4.88052854$.

revised version, 19 pages, 7 figures