共查询到20条相似文献,搜索用时 15 毫秒
1.
The main task of the paper is to demonstrate that Corollary 6 in [R.E. Hartwig, K. Spindelböck, Matrices for which A∗ and A† commute, Linear and Multilinear Algebra 14 (1984) 241-256] provides a powerful tool to investigate square matrices with complex entries. This aim is achieved, on the one hand, by obtaining several original results involving square matrices, and, on the other hand, by reestablishing some of the facts already known in the literature, often in extended and/or generalized forms. The particular attention is paid to the usefulness of the aforementioned corollary to characterize various classes of matrices and to explore matrix partial orderings. 相似文献
2.
Francesco Barioli Shaun M. Fallat Ronald L. Smith 《Linear algebra and its applications》2008,429(7):1568-1578
The minimum rank of a graph G is defined as the smallest possible rank over all symmetric matrices governed by G. It is well known that the minimum rank of a connected graph is at least the diameter of that graph. In this paper, we investigate the graphs for which equality holds between minimum rank and diameter, and completely describe the acyclic and unicyclic graphs for which this equality holds. 相似文献
3.
Necessary and sufficient conditions are derived for the matrix equality A-=PN-Q to hold, where A- and N- are generalized inverses of matrices. Some consequences and applications are also given. In particular, necessary and sufficient conditions are derived for the additive decompositions C-=A-+B- and to hold. 相似文献
4.
Baksalary and Baksalary [J.K. Baksalary, O.M. Baksalary, Nonsingularity of linear combinations of idempotent matrices, Linear Algebra Appl. 388 (2004) 25-29] proved that the nonsingularity of P1 + P2, where P1 and P2 are idempotent matrices, is equivalent to the nonsingularity of any linear combinations c1P1 + c2P2, where c1, c2 ≠ 0 and c1 + c2 ≠ 0. In the present note this result is strengthened by showing that the nullity and rank of c1P1 + c2P2 are constant. Furthermore, a simple proof of the rank formula of Groß and Trenkler [J. Groß, G. Trenkler, Nonsingularity of the difference of two oblique projectors, SIAM J. Matrix Anal. Appl. 21 (1999) 390-395] is obtained. 相似文献
5.
For an undirected simple graph G, the minimum rank among all positive semidefinite matrices with graph G is called the minimum semidefinite rank (msr) of G. In this paper, we show that the msr of a given graph may be determined from the msr of a related bipartite graph. Finding the msr of a given bipartite graph is then shown to be equivalent to determining which digraphs encode the zero/nonzero pattern of a unitary matrix. We provide an algorithm to construct unitary matrices with a certain pattern, and use previous results to give a lower bound for the msr of certain bipartite graphs. 相似文献
6.
Clément de Seguins Pazzis 《Linear algebra and its applications》2011,435(1):147-2271
Let V be a linear subspace of Mn,p(K) with codimension lesser than n, where K is an arbitrary field and n?p. In a recent work of the author, it was proven that V is always spanned by its rank p matrices unless n=p=2 and K?F2. Here, we give a sufficient condition on codim V for V to be spanned by its rank r matrices for a given r∈?1,p-1?. This involves a generalization of the Gerstenhaber theorem on linear subspaces of nilpotent matrices. 相似文献
7.
Francesco Barioli H. Tracy Hall Leslie Hogben Bryan Shader Hein van der Holst 《Linear algebra and its applications》2010,433(2):401-536
The zero forcing number Z(G), which is the minimum number of vertices in a zero forcing set of a graph G, is used to study the maximum nullity/minimum rank of the family of symmetric matrices described by G. It is shown that for a connected graph of order at least two, no vertex is in every zero forcing set. The positive semidefinite zero forcing number Z+(G) is introduced, and shown to be equal to |G|-OS(G), where OS(G) is the recently defined ordered set number that is a lower bound for minimum positive semidefinite rank. The positive semidefinite zero forcing number is applied to the computation of positive semidefinite minimum rank of certain graphs. An example of a graph for which the real positive symmetric semidefinite minimum rank is greater than the complex Hermitian positive semidefinite minimum rank is presented. 相似文献
8.
9.
Following the work of Friedman, Koerwien, Nies and Schlicht we positively answer their question whether the Scott rank of Polish metric spaces is countable. 相似文献
10.
Let F be a field and let m and n be integers with m,n?3. Let Mn denote the algebra of n×n matrices over F. In this note, we characterize mappings ψ:Mn→Mm that satisfy one of the following conditions:
- 1.
- |F|=2 or |F|>n+1, and ψ(adj(A+αB))=adj(ψ(A)+αψ(B)) for all A,B∈Mn and α∈F with ψ(In)≠0.
- 2.
- ψ is surjective and ψ(adj(A-B))=adj(ψ(A)-ψ(B)) for every A,B∈Mn.
11.
Li Qiu 《Linear algebra and its applications》2007,422(1):304-307
Let A1, … , Ak be positive semidefinite matrices and B1, … , Bk arbitrary complex matrices of order n. We show that
span{(A1x)°(A2x)°?°(Akx)|x∈Cn}=range(A1°A2°?°Ak) 相似文献
12.
For a square complex matrix F and for F∗ being its conjugate transpose, the class of matrices satisfying R(F)∩R(F∗)={0}, where R(.) denotes range (column space) of a matrix argument, is investigated. Besides identifying a number of its properties, several functions of F, such as F+F∗, (F:F∗), FF∗+F∗F, and F-F∗, are considered. Particular attention is paid to the Moore-Penrose inverses of those functions and projectors attributed to them. It is shown that some results scattered in the literature, whose complexity practically prevents them from being used to deal with real problems, can be replaced with much simpler expressions when the ranges of F and F∗ are disjoint. Furthermore, as a by-product of the derived formulae, one obtains a variety of relevant facts concerning, for instance, rank and range. 相似文献
13.
14.
Let Mn be the algebra of all n×n matrix over a field F, A a rank one matrix in Mn. In this article it is shown that if a bilinear map ? from Mn×Mn to Mn satisfies the condition that ?(u,v)=?(I,A) whenever u·v=A, then there exists a linear map φ from Mn to Mn such that . If ? is further assumed to be symmetric then there exists a matrix B such that ?(x,y)=tr(xy)B for all x,y∈Mn. Applying the main result we prove that if a linear map on Mn is desirable at a rank one matrix then it is a derivation, and if an invertible linear map on Mn is automorphisable at a rank one matrix then it is an automorphism. In other words, each rank one matrix in Mn is an all-desirable point and an all-automorphisable point, respectively. 相似文献
15.
Clément de Seguins Pazzis 《Linear algebra and its applications》2010,433(4):843-866
In a recent article, we gave a full characterization of matrices that can be decomposed as linear combinations of two idempotents with prescribed coefficients. In this one, we use those results to improve on a recent theorem of Rabanovich: we establish that every square matrix is a linear combination of three idempotents (for an arbitrary coefficient field rather than just one of characteristic 0). 相似文献
16.
Lon H. Mitchell 《Linear algebra and its applications》2011,435(6):1311-1314
In this note, we combine a number of recent ideas to give new results on the graph complement conjecture for minimum semidefinite rank. 相似文献
17.
Jan R. Magnus 《Journal of multivariate analysis》2010,101(9):2200-2206
We discuss how to generalize the concept of vector derivative to matrix derivative, propose two definitions, a ‘broad’ and a ‘narrow’ one, compare the two definitions, and argue in favor of the narrow definition. 相似文献
18.
Let H be the real quaternion algebra and Hn×m denote the set of all n×m matrices over H. Let P∈Hn×n and Q∈Hm×m be involutions, i.e., P2=I,Q2=I. A matrix A∈Hn×m is said to be (P,Q)-symmetric if A=PAQ. This paper studies the system of linear real quaternion matrix equations
19.
Let K be a field and let Mm×n(K) denote the space of m×n matrices over K. We investigate properties of a subspace M of Mm×n(K) of dimension n(m-r+1) in which each non-zero element of M has rank at least r and enumerate the number of elements of a given rank in M when K is finite. We also provide an upper bound for the dimension of a constant rank r subspace of Mm×n(K) when K is finite and give non-trivial examples to show that our bound is optimal in some cases. We include a similar a bound for the maximum dimension of a constant rank subspace of skew-symmetric matrices over a finite field. 相似文献
20.
Let Mm,n(B) be the semimodule of all m×n Boolean matrices where B is the Boolean algebra with two elements. Let k be a positive integer such that 2?k?min(m,n). Let B(m,n,k) denote the subsemimodule of Mm,n(B) spanned by the set of all rank k matrices. We show that if T is a bijective linear mapping on B(m,n,k), then there exist permutation matrices P and Q such that T(A)=PAQ for all A∈B(m,n,k) or m=n and T(A)=PAtQ for all A∈B(m,n,k). This result follows from a more general theorem we prove concerning the structure of linear mappings on B(m,n,k) that preserve both the weight of each matrix and rank one matrices of weight k2. Here the weight of a Boolean matrix is the number of its nonzero entries. 相似文献