偏序集的内蕴拓扑连通性北大核心

从序与拓扑的交叉考虑,进一步研究偏序集在多种内蕴拓扑下的连通性和局部连通性.主要结果有:(1)一个偏序集是序连通的当且仅当它赋予Alexandrov拓扑是连通的,也当且仅当它赋予Scott拓扑是连通的;(2)每一偏序集赋予Alexandrov拓扑是局部连通的,每一偏序集赋予Scott拓扑是局部连通的;(3)如果拓扑空间的特殊化偏序集序连通,则该拓扑空间是连通的;(4)构造反例说明了存在偏序集赋予下拓扑后是连通空间,但该偏序集本身不是序连通的.     

偏序集上的测度拓扑和全测度

在偏序集上引入测度拓扑和全测度概念,研究其性质以及与其它内蕴拓扑间的众多关系。主要结果有:连续偏序集的测度拓扑实际上是由其上的任一全测度所决定且可由它的定向完备化上的测度拓扑和全测度分别限制得到;当连续偏序集还是D om a in时,其上的测度拓扑与μ拓扑一致;连续偏序集有可数基当且仅当其上的测度拓扑是可分的;一个网如果测度收敛则存在最终上确界;任一ω连续偏序集上都存在全测度。     

伪超连续偏序集

引入了伪超连续偏序集和伪超代数偏序集的概念,讨论了它们的一些基本性质,给出了它们的若干刻画,特别是基于区间拓扑、某种特殊二元关系的刻画和内蕴式刻画.     

关于连续偏序集的一个刻画定理(英文)

本文给出了连续偏序集的一个刻画定理及相应的代数偏序集刻画定理.进一步得出连续偏序集P关于其Scott拓扑是局部紧的,而且OFilt(P)是一个domain.这推广了关于dcpo的对应结果.     

5元素集合上T_0拓扑总数的计算

利用有限偏序集上的几个重要结果并借助于拓扑空间对应的特殊化序与拓扑之间的关系计算得出5元素集合上T0拓扑总数为4231,拓扑总数为6942.     

6元素集合上T0拓扑总数的计算

文中证明了有限预序集与有限偏序集的一些性质,并基于有限集上的拓扑和其上预序的一一对应关系,利用这些性质通过对极小元和极大元个数进行分类讨论,以一种有别于计算机算法而又容易理解的计算方法得出6元素集合上的T₀拓扑总数为130023.     

可数S_2-拟连续偏序集北大核心CSCD

作为广义可数逼近偏序集与S2-拟连续偏序集的共同推广,引入了可数S2-拟连续偏序集的概念并讨论了它的一些性质.本文的主要结果:(1)可数S2-拟连续偏序集上的可数way below关系满足插入性质;(2)可数S2-拟连续偏序集关于其上的弱σ-Scott拓扑为局部紧致的可数sober空间;(3)偏序集P为可数S2-连续偏序集当且仅当P为可数S2-交连续的可数S2-拟连续偏序集.     

模糊偏序集上理想完备的幂等性

主要讨论模糊偏序集上理想完备性的本质.并得到以下结论:模糊偏序集的理想完备是幂等的当且仅当理想完备上的广义Scott拓扑与Alexandroff拓扑是一致的.     

偏序集的φ-(交)连续性及其主理想刻画

证明φ-完备偏序集是（强）P连续的当且仅当该偏序集的任一主理想是（强）φ-连续的。在φ-完备偏序集中利用φ-S集族生成f-Scott拓扑，并由此引入φ-交连续偏序集概念。证明φ-完备偏序集是P交连续的当且仅当该偏序集的任一主理想是φ-交连续的。     

关于自然偏序集的自然连续性

在自然偏序集中引入自然way-below关系,定义自然偏序集的自然连续性.证明在自然连续的自然偏序集上,自然way-below关系具有插入性,自然Scott开集格是完全分配格.利用(&)*收敛刻画了自然偏序集上的自然way-below关系,自然Scott拓扑和自然连续性.     

偏序集上的测度拓扑与稠拓扑

In this paper,the concepts of the essential topology and the density topology of dcpos are generalized to the setting of general posets.Basic properties of the essential topology and relations with other intrinsic topologies are explored.Comparisons between the density topology and the measurement topology are made.Via the essential topology,the density topology and the measurement topology,we obtain properties and characterizations of bases of continuous posets.We also provide some new conditions for a continuous poset to be an algebraic poset.     

Order topology and bi-Scott topology on a poset

In this paper, some properties of order topology and bi-Scott topology on a poset are obtained. Order-convergence in posets is further studied. Especially, a sufficient and necessary condition for order-convergence to be topological is given for some kind of posets.     

Quasicontinuity of Posets via Scott Topology and Sobrification

In this paper, posets which may not be dcpos are considered. In terms of the Scott topology on posets, the new concept of quasicontinuous posets is introduced. Some properties and characterizations of quasicontinuous posets are examined. The main results are: (1) a poset is quasicontinuous iff the lattice of all Scott open sets is a hypercontinuous lattice; (2) the directed completions of quasicontinuous posets are quasicontinuous domains; (3) A poset is continuous iff it is quasicontinuous and meet continuous, generalizing the relevant result for dcpos. Supported by the NSF of China (10371106, 10410638) and by the Fund (S0667-082) from Nanjing University of Aeronautics and Astronautics.     

The Number of Unlabeled Orders on Fourteen Elements

Lacking an explicit formula for the numbers T ₀(n) of all order relations (equivalently: T ₀ topologies) on n elements, those numbers have been explored only up to n=13 (unlabeled posets) and n=15 (labeled posets), respectively.In a new approach, we used an orderly algorithm to (i) generate each unlabeled poset on up to 14 elements and (ii) collect enough information about the posets on 13 elements to be able to compute the number of labeled posets on 16 elements by means of a formula by Erné. Unlike other methods, our algorithm avoids isomorphism tests and can therefore be parallelized quite easily. The underlying principle of successively adding new elements to small objects is applicable to lattices and other kinds of order structures, too.     

Compact Compatible Topologies for Posets and Graphs

A topology on the vertex set of a comparability graph G is said to be compatible (respectively, weakly compatible) with G if each induced subgraph (respectively, each finite induced subgraph) is topologically connected if and only it it is graph-connected; a weakly compatible topology on the vertex set of a graph completely determines the graph structure. We consider here the problem of deciding whether or not a comparability graph has a compact compatible or weakly compatible topology and in the case of graphs with small cycles, hence in the case of trees, we give a characterization.     

Finite Eulerian posets which are binomial, Sheffer or triangular

In this paper we study finite Eulerian posets which are binomial, Sheffer or triangular. These important classes of posets are related to the theory of generating functions and to geometry. The results of this paper are organized as follows:

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We completely determine the structure of Eulerian binomial posets and, as a conclusion, we are able to classify factorial functions of Eulerian binomial posets.

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We give an almost complete classification of factorial functions of Eulerian Sheffer posets by dividing the original question into several cases.

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In most cases above, we completely determine the structure of Eulerian Sheffer posets, a result stronger than just classifying factorial functions of these Eulerian Sheffer posets.

We also study Eulerian triangular posets. This paper answers questions posed by R. Ehrenborg and M. Readdy. This research is also motivated by the work of R. Stanley about recognizing the boolean lattice by looking at smaller intervals.     

A Note on the Homology of Signed Posets

Let S be a signed poset in the sense of Reiner [4]. Fischer [2] defines the homology of S, in terms of a partial ordering P (S) associated to S, to be the homology of a certain subcomplex of the chain complex of P (S).In this paper we show that if P (S) is Cohen-Macaulay and S has rank n, then the homology of S vanishes for degrees outside the interval [n/2, n].Research partially supported by the National Science Foundation and the John Simon Guggenheim Foundation.     

Signed differential posets and sign-imbalance

We study signed differential posets, a signed version of differential posets. These posets satisfy enumerative identities which are signed analogues of those satisfied by differential posets. Our main motivations are the sign-imbalance identities for partition shapes originally conjectured by Stanley, now proven in [T. Lam, Growth diagrams, domino insertion and sign-imbalance, J. Combin. Theory Ser. A 107 (2004) 87-115; A. Reifergerste, Permutation sign under the Robinson-Schensted-Knuth correspondence, Ann. Comb. 8 (2004) 103-112; J. Sjöstrand, On the sign-imbalance of partition shapes, J. Combin. Theory Ser. A 111 (2005) 190-203]. We show that these identities result from a signed differential poset structure on Young's lattice, and explain similar identities for Fibonacci shapes.