Some facets of the polytope of even permutation matrices Original Research Article

We describe a class of facets of the polytope of convex combinations of the collection of even n×n permutation matrices. As a consequence, we prove the conjecture of Brualdi and Liu [J. Combin. Theory Ser. A 57 (1991) 243] that the number of facets of the polytope is not bounded by a polynomial in n.