PO_n的局部极大幂等元生成的子半群

研究了有限链上的部分保序变换半群PO_n.通过对其幂等元的分析,获得了PO_n的局部极大幂等元生成的子半群的结构与分类.     

幂等余 Quantale

讨论了幂等余Quantale与左纯元、子余Quantale的一些相关性质,发现幂等余Quantale的左纯元构成的集合是对应的子余Quantale;每个幂等余Quantale都可有一个核映射与子余Quantale保持对应关系;并且幂等余Quantale与核映射,左右纯元,Frame等都有一定关系.     

Mappings preserving the idempotency of products of operators

We obtain a general form of a surjective (not assumed additive) mapping φ, preserving the nonzero idempotency of a certain product, being defined (a) on the algebra of all bounded linear operators B(X), where X is at least three-dimensional real or complex Banach space, (b) on the set of all rank-one idempotents in B(X) and (c) on the set of all idempotents in B(X). In any of the cases it turns out that φ is additive and either multiplicative or antimultiplicative.     

The parallel refinement of weakening idempotent pair

In this paper, we invent the parallel refinement, which refines the weakening idempotent pair into the positive and contractive one preserving K-theory information. We conduct a quantitative matrix analysis for this refinement, which shows that this refinement is more effective when we derive almost projection from weakening idempotent pairs.     

On the maximal subgroup of the sandwich semigroup of generalized circulant Boolean matrices

Let n be a positive integer, and C _n (r) the set of all n × n r-circulant matrices over the Boolean algebra B = {0, 1}, . For any fixed r-circulant matrix C (C ≠ 0) in G _n , we define an operation “*” in G _n as follows: A * B = ACB for any A, B in G _n , where ACB is the usual product of Boolean matrices. Then (G _n , *) is a semigroup. We denote this semigroup by G _n (C) and call it the sandwich semigroup of generalized circulant Boolean matrices with sandwich matrix C. Let F be an idempotent element in G _n (C) and M(F) the maximal subgroup in G _n (C) containing the idempotent element F. In this paper, the elements in M(F) are characterized and an algorithm to determine all the elements in M(F) is given.     

关于幂等元之差的可逆性

本文研究在一个有单位元的环中两个幂等元之差的可逆性问题,利用幂等元的性质,得到了两个幂等元之差可逆的几个充分必要条件,并给出了在矩阵环中的几个应用.     

Symmetries that latin squares inherit from 1‐factorizations

A 1‐factorization of a graph is a decomposition of the graph into edge disjoint perfect matchings. There is a well‐known method, which we call the ??‐construction, for building a 1‐factorization of K_n,n from a 1‐factorization of K_{n + 1}. The 1‐factorization of K_n,n can be written as a latin square of order n. The ??‐construction has been used, among other things, to make perfect 1‐factorizations, subsquare‐free latin squares, and atomic latin squares. This paper studies the relationship between the factorizations involved in the ??‐construction. In particular, we show how symmetries (automorphisms) of the starting factorization are inherited as symmetries by the end product, either as automorphisms of the factorization or as autotopies of the latin square. Suppose that the ??‐construction produces a latin square L from a 1‐factorization F of K_{n + 1}. We show that the main class of L determines the isomorphism class of F, although the converse is false. We also prove a number of restrictions on the symmetries (autotopies and paratopies) which L may possess, many of which are simple consequences of the fact that L must be symmetric (in the usual matrix sense) and idempotent. In some circumstances, these restrictions are tight enough to ensure that L has trivial autotopy group. Finally, we give a cubic time algorithm for deciding whether a main class of latin squares contains any square derived from the ??‐construction. The algorithm also detects symmetric squares and totally symmetric squares (latin squares that equal their six conjugates). © 2005 Wiley Periodicals, Inc. J Combin Designs 13: 157–172, 2005.