A differential poset is a partially ordered set with raising and lowering operators U and D which satisfy the commutation relation DU−UD = rI for some constant r. This notion may be generalized to deal with the case in which there exist sequences of constants {qn}n≥0 and {rn}n≥0 such that for any poset element x of rank n, DU(x) = qnUD(x)+rnx. Here, we introduce natural raising and lowering ope...

nets, useful topological tools, used to generalize certainconcepts that may only be general enough in the context of metricspaces. in this work we introduce this concept in an $s$-poset, aposet with an action of a posemigroup $s$ on it whichis a very useful structure in computer sciences and interestingfor mathematicians, and give the the concept of $s$-net. using $s$-nets and itsconvergency we...

This paper studies the poset of eigenspaces of elements of an imprimitive unitary reflection group, for a fixed eigenvalue, ordered by the reverse of inclusion. The study of this poset is suggested by the eigenspace theory of Springer and Lehrer. The posets are shown to be isomorphic to certain subposets of Dowling lattices (the ”d-divisible, k-evenly coloured Dowling lattices”). This enables u...

The Dushnik-Miller dimension of a poset ≤ is the minimal number d of linear extensions ≤1, . . . ,≤d of ≤ such that ≤ is the intersection of ≤1, . . . ,≤d. Supremum sections are simplicial complexes introduced by Scarf [13] and are linked to the Dushnik-Miller as follows: the inclusion poset of a simplicial complex is of Dushnik-Miller dimension at most d if and only if it is included in a supr...

We use a variety of combinatorial techniques to prove several theorems concerning fractional dimension of partially ordered sets. In particular, we settle a conjecture of Brightwell and Scheinerman by showing that the fractional dimension of a poset is never more than the maximum degree plus one. Furthermore, when the maximum degree k is at least two, we show that equality holds if and only if ...

A sectionally pseudocomplemented poset P is one which has the top element and in which every principal order filter is a pseudocomplemented poset. The sectional pseudocomplements give rise to an implication-like operation on P which coincides with the relative pseudocomplementation if P is relatively psudocomplemented. We characterise this operation and study some elementary properties of upper...

An on-line chain partitioning algorithm receives a poset, one element at time, and irrevocably assigns the to of chains. Over 30 years ago, Szemerédi proved that any could be forced use $$\left( {\begin{array}{c}w+1\\ 2\end{array}}\right)$$ chains partition poset width w. The maximum number can on remains unknown. In survey paper by Bosek et al., it is shown Szemerédi’s argument improved obtain...

We provide a method to construct a type of orthomodular structure known as an orthoalgebra from the direct product decompositions of an object in a category that has finite products and whose ternary product diagrams give rise to certain pushouts. This generalizes a method to construct an orthomodular poset from the direct product decompositions of familiar mathematical structures such as non-e...

We introduce a family of posets which generate Lie poset subalgebras $$A_{n-1}=\mathfrak {sl}(n)$$ whose index can be realized topologically. In particular, if $$\mathcal {P}$$ is such toral poset, then it has simplicial realization homotopic to wedge sum d one-spheres, where the corresponding type-A algebra $$\mathfrak {g}_A(\mathcal {P})$$ . Moreover, when Frobenius, its spectrum binary, that...

Let Bn be the poset generated by the subsets of [n] with the inclusion as relation and let P be a nite poset. We want to embed P into Bn as many times as possible such that the subsets in di erent copies are incomparable. The maximum number of such embeddings is asymptotically determined for all nite posets P as 1 t(P ) ( n bn/2c ) , where t(P ) denotes the minimal size of the convex hull of a ...