For a locally quasi-convex topological abelian group (G, τ), we study the poset C (G, τ) of all locally quasi-convex topologies on G that are compatible with τ (i.e., have the same dual as (G, τ)) ordered by inclusion. Obviously, this poset has always a bottom element, namely the weak topology σ(G, Ĝ). Whether it has also a top element is an open question. We study both quantitative aspects of ...

Let f(n) be the largest integer such that every poset on n elements has a 2-dimensional subposet on f(n) elements. What is the asymptotics of f(n)? It is easy to see that f(n) > n. We improve the best known upper bound and show f(n) = O(n). For higher dimensions, we show fd(n) = O ( n d d+1 ) , where fd(n) is the largest integer such that every poset on n elements has a d-dimensional subposet o...

Let D denote the partially ordered sets of homomorphism classes of finite directed graphs, ordered by the homomorphism relation. Order theoretic properties of this poset have been studied extensively, and have interesting connections to familiar graph properties and parameters. This paper studies the generalized duality pairs in D: it gives a new, short proof for the Foniok Nešetřil Tardif theo...

With a nite graph G V E we associate a partially ordered set P X P with X V E and x e in P if and only if x is an endpoint of e in G This poset is called the incidence poset of G In this paper we consider the function M p d de ned for p d as the maximum number of edges a graph G can have when it has p vertices and the dimension of its incidence poset is at most d It is easy to see that M p p as...

With a finite graph G = (V,E), we associate a partially ordered set P = (X, P) with X = V U E and x < e in P if and only if x is an endpoint of e in G. This poset is called the incidence poset of G. In this paper, we consider the function M ( p , d ) defined for p, d~>2 as the maximum number of edges a graph G can have when it has p vertices and the dimension of its incidence poset is at most d...

Given a partially ordered set P = (X; P), a function F which assigns to each x 2 X a set F (x) so that x y in P if and only if F (x) F (y) is called an inclusion representation. Every poset has such a representation, so it is natural to consider restrictions on the nature of the images of the function F. In this paper, we consider inclusion representations assigning to each x 2 X a sphere in R ...

The concept of signed poset has recently been introduced by V. Reiner as a generalization of that of ordinary poset (partially ordered set). We consider the problem of finding a minimum-weight ideal of a signed poset. We show a representation theorem that there exists a bijection between the set of all the ideals of a signed poset and the set of all the "reduced ideals" (defined here) of the as...

We give a complete classification of the factorial functions of Eulerian binomial posets. The factorial function B(n) either coincides with n!, the factorial function of the infinite Boolean algebra, or 2n−1, the factorial function of the infinite butterfly poset. We also classify the factorial functions for Eulerian Sheffer posets. An Eulerian Sheffer poset with binomial factorial function B(n...

Let P = ({1, 2, . . . , n,≤) be a poset that is an union of disjoint chains of the same length and V = Fq be the space of N -tuples over the finite field Fq. Let Vi = F ki q , 1 ≤ i ≤ n, be a family of finitedimensional linear spaces such that k1 + k2 + . . . + kn = N and let V = V1⊕V2⊕ . . .⊕Vn endow with the poset block metric d(P,π) induced by the poset P and the partition π = (k1, k2, . . ....

A simplicial poset P (also called a boolean poset and a poset of boolean type) is a finite poset with a smallest element 0̂ such that every interval [0̂, y] for y ∈ P is a boolean algebra, i.e., [0̂, y] is isomorphic to the set of all subsets of a finite set, ordered by inclusion. The set of all faces of a (finite) simplicial complex with empty set added forms a simplicial poset ordered by inclusi...