Degrees of freedom versus dimension for containment orders

Given a family of sets L, where the sets in L admit k ‘degrees of freedom’, we prove that not all (k+1)-dimensional posets are containment posets of sets in L. Our results depend on the following enumerative result of independent interest: Let P(n, k) denote the number of partially ordered sets on n labeled elements of dimension k. We show that log P(n, k)∼nk log n where k is fixed and n is large.