In an earlier work we described Gröbner bases of the ideal of polynomials over a field, which vanish on the set of characterisic vectors v ∈ {0, 1} n of the complete d unifom set family over the ground set [n]. In particular, it turns out that the standard monomials of the above ideal are ballot monomials. We give here a partial extension of this fact. A set family is a linear Sperner system if the characteristic vectors satisfy a linear equation a 1 v 1 + · · · + a n v n = k, where the a i and k are positive integers. We prove that the lexicographic standard monomials for linear Sperner systems are also ballot monomials, provided that 0 < a 1 ≤ a 2 ≤ · · · ≤ a n . As an application, we confirm a conjecture of Frankl in the special case of linear Sperner systems.
2010