范畴MΔ中的正合列

本文研究域上矩阵给出的范畴,给出了正合性的等价刻画,提出了将正合列理论应用于矩阵论的途径．     

范畴_Δ中的正合列

本文研究域上矩阵给出的范畴,给出了正合性的等价刻画,提出了将正合列理论应用于矩阵论的途径．     

p－除环上子空间的交与和

本文讨论ｐ－除环上子空间的交与和的关系，用Ａｂｅｌ范畴中裂正合序列的性质证明矩阵秩的恒等式和维数公式．     

范畴()△中的正合列

本文研究域上矩阵给出的范畴,给出了正合性的等价刻画,提出了将正合列理论应用于矩阵论的途径.     

四元数向量和矩阵的秩

在四元数和四元数向量、矩阵空间上引入三种不同的实表示法则，将四元数列向量的左右线性相关性问题转换成实数域上向量的线性相关问题，由此获得用实矩阵的秩代替四元数矩阵列左秩和列右秩计算方法，同时得出四元数矩阵可逆的一些充要条件和一些新的四元数行列式定义．     

非单位κ-代数的局部循环同调及切除定理

本文定义了单位过滤k-代数和非单位过滤k-代数的局部Hochschild同调和局部循环同调,给出 了它们之间的局部Connes长正合列．进一步利用循环同调来计算局部循环同调的短正合列公式,讨论 了关于过滤k-代数局部循环同调的切除定理．     

L-S-系中的正合列

经典模论中,正合列是研究函子问题的基本工具。在半群S-系理论中,正合列对函子的研究同样起着重要作用。用类似L-模中的方法,给出L-S-系及其正合列的定义,得到已知序列正合的一个必要条。另外,还定义L-S-系中两个短正合列之间的弱同构与同构,并得到在一般S-系范畴中短正合列μ1→μ1Цμ2→μ2弱同构于短正合列μ1→η→μ2的充分条件。     

半环上矩阵的秩和坡上矩阵可逆的条件

研究了交换半环上矩阵的秩和坡上矩阵的可逆条件.利用Beasley的引理以及不变式,获得了交换半环上正则矩阵的行秩、列秩与Schein秩三者相等,以及坡上矩阵可逆的充要条件.推广模糊代数和分配格上矩阵的结果.     

在具有终对象的范畴内的正合列

本文对于具有终对象的范畴定义了四个一般正合列．在Ａｂｅｌ范畴同调代数里，对于具有零对象的任何范畴四个一般正合列与通常的正合列相同     

p—除环上子空间的交与和

本文讨论Ｐ－除环上 间的交与和的关系。用Ａｂｅｌ范畴中裂正合序列的性质证明矩阵秩的恒等式和维数公式。     

BIFUNLTORS AND THE DIAGONAL EXACT SEQUENCES OF A CYLINDER-WEB DIAGRAM

The doubly infinite diagram of exact sequences that an additive bifunctor T associates with a pair of short exact sequences can be regarded as a web diagram lying on the surface of a cylinder. The diagram has six diagonal sequences involving two graded derived functors that arise through the failure of T to preserve pull-backs respectively push-outs. In the case T = Hom(-,-) one of the diagonal sequences is equivalent to the bivariant Hom-Ext sequence studied by Pressmann [4].     

非交换主理想整环上分块矩阵的秩

本文从非交换主理想整环Ｒ上矩阵Ａ的秩与它在Ｒ所嵌入的商除环Ｋ上的秩间的关系着手，证得了Ｒ上分块矩阵秩的一些结果，因此也解决了［１］中关于ｐ￣一除环上矩阵秩的一个猜想．     

关于除环上分块矩阵秩的等式

本文使用双矩阵分解方法研究除环上分块矩阵秩的等式,给出了Marsaglia-Styan公式一个新的证明并获得了一些新的秩等式的刻划.     

Rank of <Emphasis Type="Italic">K</Emphasis><Subscript>2</Subscript> of elliptic curves

We prove that (i) rank(K2(E)) 1 for all elliptic curves E defined over Q with a rational torsion point of exact order N 4; (ii) rank(K2(E)) 1 for all but at most one R-isomorphism class of elliptic curves E defined over Q with a rational torsion point of exact order 3. We give some sufficient conditions for rank(K2(EZ)) 1.     

Heuristics for exact nonnegative matrix factorization

The exact nonnegative matrix factorization (exact NMF) problem is the following: given an m-by-n nonnegative matrix X and a factorization rank r, find, if possible, an m-by-r nonnegative matrix W and an r-by-n nonnegative matrix H such that \(X = WH\). In this paper, we propose two heuristics for exact NMF, one inspired from simulated annealing and the other from the greedy randomized adaptive search procedure. We show empirically that these two heuristics are able to compute exact nonnegative factorizations for several classes of nonnegative matrices (namely, linear Euclidean distance matrices, slack matrices, unique-disjointness matrices, and randomly generated matrices) and as such demonstrate their superiority over standard multi-start strategies. We also consider a hybridization between these two heuristics that allows us to combine the advantages of both methods. Finally, we discuss the use of these heuristics to gain insight on the behavior of the nonnegative rank, i.e., the minimum factorization rank such that an exact NMF exists. In particular, we disprove a conjecture on the nonnegative rank of a Kronecker product, propose a new upper bound on the extension complexity of generic n-gons and conjecture the exact value of (i) the extension complexity of regular n-gons and (ii) the nonnegative rank of a submatrix of the slack matrix of the correlation polytope.     

A comparison of nonnegative real ranks and their preservers

This paper concerns three notions of rank of matrices over semirings; real rank, semiring rank and column rank. These three rank functions are the same over subfields of reals but differ for matrices over subsemirings of nonnegative reals. We investigate the largest values of r for which the real rank and semiring rank, real rank and column rank of all m×n matrices over a given semiring are both r, respectively. We also characterize the linear operators which preserve the column rank of matrices over certain subsemirings of the nonnegative reals.     

Orthogonal representations over finite fields and the chromatic number of graphs

We study the relationship between the minimum dimension of an orthogonal representation of a graph over a finite field and the chromatic number of its complement. It turns out that for some classes of matrices defined by a graph the 3-colorability problem is equivalent to deciding whether the class defined by the graph contains a matrix of rank 3 or not. This implies the NP-hardness of determining the minimum rank of a matrix in such a class. Finally we give for any class of matrices defined by a graph that is interesting in this respect a reduction of the 3-colorability problem to the problem of deciding whether or not this class contains a matrix of rank equal to three.The author is financially supported by the Cooperation Centre Tilburg and Eindhoven Universities.     

A comparison of nonnegative real ranks and their preservers

This paper concerns three notions of rank of matrices over semirings; real rank, semiring rank and column rank. These three rank functions are the same over subfields of reals but differ for matrices over subsemirings of nonnegative reals. We investigate the largest values of r for which the real rank and semiring rank, real rank and column rank of all m×n matrices over a given semiring are both r, respectively. We also characterize the linear operators which preserve the column rank of matrices over certain subsemirings of the nonnegative reals.     

The bilinear complexity and practical algorithms for matrix multiplication

A method for deriving bilinear algorithms for matrix multiplication is proposed. New estimates for the bilinear complexity of a number of problems of the exact and approximate multiplication of rectangular matrices are obtained. In particular, the estimate for the boundary rank of multiplying 3 × 3 matrices is improved and a practical algorithm for the exact multiplication of square n × n matrices is proposed. The asymptotic arithmetic complexity of this algorithm is O(n ^2.7743).