Characterization of sign patterns that allow diagonalizability has been a long-standing open problem.In this paper,we obtain some sufficient and/or necessary conditions for a sign pattern to allow diagonalizability.Mo...Characterization of sign patterns that allow diagonalizability has been a long-standing open problem.In this paper,we obtain some sufficient and/or necessary conditions for a sign pattern to allow diagonalizability.Moreover,we determine how many entries need to be changed to obtain a matrix B′∈Q(A)with rank MR(A)from a matrix B∈Q(A)with rank mr(A).Finally,we also obtain some results on a sign pattern matrix in Frobenius normal form that allows diagonalizability.展开更多
A sign pattern is a matrix whose entries are from the set {+,-,0}. Associated with each sign pattern A of order n is a qualitative class of A,defined by Q(A). For a symmetric sign pattern A of order n,the inertia of A...A sign pattern is a matrix whose entries are from the set {+,-,0}. Associated with each sign pattern A of order n is a qualitative class of A,defined by Q(A). For a symmetric sign pattern A of order n,the inertia of A is a set i(A)={i(B)=(i +(B),i -(B),i 0(B))|B=B T∈ Q(A)},where i +(B) (respectively,i -(B),i 0(B)) denotes the number of positive (respectively,negative,zero) eigenvalues. That the symmetric sign pattern A requires unique intertia means i(B 1)=i(B 2) for all real symmetric matrices B 1,B 2∈Q(A).The purpose of this paper is to characterize double star and cycle sign patterns that require unique inertia. Further,their unique inertia is also obtained.展开更多
A sign pattern(matrix)is a matrix whose entries are the symbols+,-and 0.Foran n×n sign pattern matrix A,the sign pattern class of A,denoted by Q(A),is the set ofall n×n real matrices whose entries have signs...A sign pattern(matrix)is a matrix whose entries are the symbols+,-and 0.Foran n×n sign pattern matrix A,the sign pattern class of A,denoted by Q(A),is the set ofall n×n real matrices whose entries have signs indicated by the corresponding entries of A.We say that a sign pattern matrix A requires a matrix property P if every real matrix in Q(A)has the property P.A matrix with all distinct eigenvalues has many nice展开更多
In qualitative and combinatorial matrix theory,we study properties of a matrix basedon qualitative information,such as the signs of entries in the matrix.A matrix whose en-tries are from the set{+,-,0}is called a sign...In qualitative and combinatorial matrix theory,we study properties of a matrix basedon qualitative information,such as the signs of entries in the matrix.A matrix whose en-tries are from the set{+,-,0}is called a sign pattern matrix (or sign pattern).For a re-al matrix B,by sgn (B) we mean the sign pattern matrix in which each positive (respec-tively,negative,zero) entry of B is replaced by+(respectively,-,0).If A is an展开更多
Let P be a property referring to a real matrix. For a sign pattern A, if there exists a real matrix B in the qualitative class of A such that B has property P, then we say A allows P. Three cases that A allows an M m...Let P be a property referring to a real matrix. For a sign pattern A, if there exists a real matrix B in the qualitative class of A such that B has property P, then we say A allows P. Three cases that A allows an M matrix, an inverse M matrix and a P 0 matrix are considered. The complete characterizations are obtained.展开更多
Finding the necessary and sufficient conditions for a sign pattern to allow diagonalizability is an open problem. In this paper,we identify sign patterns of up to four orders that allow diagonalizability.
Let S be a nonempty, proper subset of all possible refined inertias of real matrices of order n. The set S is a critical set of refined inertias for irreducible sign patterns of order n,if for each n × n irreduci...Let S be a nonempty, proper subset of all possible refined inertias of real matrices of order n. The set S is a critical set of refined inertias for irreducible sign patterns of order n,if for each n × n irreducible sign pattern A, the condition S ? ri(A) is sufficient for A to be refined inertially arbitrary. If no proper subset of S is a critical set of refined inertias, then S is a minimal critical set of refined inertias for irreducible sign patterns of order n.All minimal critical sets of refined inertias for full sign patterns of order 3 have been identified in [Wei GAO, Zhongshan LI, Lihua ZHANG, The minimal critical sets of refined inertias for 3×3 full sign patterns, Linear Algebra Appl. 458(2014), 183–196]. In this paper, the minimal critical sets of refined inertias for irreducible sign patterns of order 3 are identified.展开更多
For a symmetric sign pattern S1 the inertia set of S is defined to be the set of all ordered triples si（S） = {i（A） ： A = A^T ∈ Q（S）} Consider the n × n sign pattern Sn, where Sn is the pattern with zero e...For a symmetric sign pattern S1 the inertia set of S is defined to be the set of all ordered triples si（S） = {i（A） ： A = A^T ∈ Q（S）} Consider the n × n sign pattern Sn, where Sn is the pattern with zero entry （i,j） for 1 ≤ i = j ≤ n or｜i -j｜=n- 1 and positive entry otherwise. In this paper, it is proved that si（Sn） = {（n1, n2, n - n1 - n2）｜n1≥ 1 and n2 ≥ 2} for n ≥ 4.展开更多
An n × n complex sign pattern （ray pattern） S is said to be spectrally arbitrary if for every monic nth degree polynomial f（λ） with coefficients from C, there is a complex matrix in the complex sign pattern ...An n × n complex sign pattern （ray pattern） S is said to be spectrally arbitrary if for every monic nth degree polynomial f（λ） with coefficients from C, there is a complex matrix in the complex sign pattern class （ray pattern class） of 3 such that its characteristic polynomial is f（λ）. We derive the Nilpotent-Centralizer methods for spectrally arbitrary complex sign patterns and ray patterns, respectively. We find that the Nilpotent-Centralizer methods for three kinds of patterns （sign pattern, complex sign pattern, ray pattern） are the same in form.展开更多
Let A be a real matrix or a sign pattern of order n. N_-(A) denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A~2≤0, then (N_-(A~2)≤)(...Let A be a real matrix or a sign pattern of order n. N_-(A) denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A~2≤0, then (N_-(A~2)≤)(n-1)~2+1. Now the conjecture is proved to be true when A is reducible or a matrix of order n≤3 and some sufficient conditions for N_-(A~2)≤(n-1)~2+1 are given. It is also proved that N_-(A~2)≤n~2-(4n+)5 when A is a reducible combinatorially symmetric sign pattern such that A~2≤0, and the extreme sign patterns are characterized.展开更多
A sign pattern is a matrix whose entries axe from the set {＋,-,0}. A sign pattern is a generalized star sign pattern if it is combinatorial symmetric and its graph is a generalized star graph. The purpose of this pap...A sign pattern is a matrix whose entries axe from the set {＋,-,0}. A sign pattern is a generalized star sign pattern if it is combinatorial symmetric and its graph is a generalized star graph. The purpose of this paper is to obtain the bound of minimal rank of any generalized star sign pattern （possibly with nonzero diagonal entries）.展开更多
A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative ...A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative entries that can occur in A whenever Ak≤0. Finally, we give a necessity and sufficiency condition for A2≤0.展开更多
Assume that S is an nth-order complex sign pattern.If for every nth degree complex coefficient polynomial f(λ)with a leading coefficient of 1,there exists a complex matrix C∈Q(S)such that the characteristic polynomi...Assume that S is an nth-order complex sign pattern.If for every nth degree complex coefficient polynomial f(λ)with a leading coefficient of 1,there exists a complex matrix C∈Q(S)such that the characteristic polynomial of C is f(λ),then S is called a spectrally arbitrary complex sign pattern.That is,if the spectrum of nth-order complex sign pattern S is a set comprised of all spectra of nth-order complex matrices,then S is called a spectrally arbitrary complex sign pattern.This paper presents a class of spectrally arbitrary complex sign pattern with only 3n nonzero elements by adopting the method of Schur complement and row reduction.展开更多
If every monic real polynomial of degree n can be achieved as the characteristic polynomial of some matrix B∈Q(A),then sign pattern A of order n is a spectrally arbitrary pattern.A sign pattern A is minimally spectra...If every monic real polynomial of degree n can be achieved as the characteristic polynomial of some matrix B∈Q(A),then sign pattern A of order n is a spectrally arbitrary pattern.A sign pattern A is minimally spectrally arbitrary if it is spectrally arbitrary but is not spectrally arbitrary if any nonzero entry(or entries)of A is replaced by zero.In this article,we give some new sign patterns which are minimally spectrally arbitrary for order n≥9.展开更多
基金Supported by Research Project of Leshan Normal University(Grant No.LZD016)。
文摘Characterization of sign patterns that allow diagonalizability has been a long-standing open problem.In this paper,we obtain some sufficient and/or necessary conditions for a sign pattern to allow diagonalizability.Moreover,we determine how many entries need to be changed to obtain a matrix B′∈Q(A)with rank MR(A)from a matrix B∈Q(A)with rank mr(A).Finally,we also obtain some results on a sign pattern matrix in Frobenius normal form that allows diagonalizability.
基金Supported by Shanxi Natural Science Foundation (2 0 0 1 1 0 0 6 )
文摘A sign pattern is a matrix whose entries are from the set {+,-,0}. Associated with each sign pattern A of order n is a qualitative class of A,defined by Q(A). For a symmetric sign pattern A of order n,the inertia of A is a set i(A)={i(B)=(i +(B),i -(B),i 0(B))|B=B T∈ Q(A)},where i +(B) (respectively,i -(B),i 0(B)) denotes the number of positive (respectively,negative,zero) eigenvalues. That the symmetric sign pattern A requires unique intertia means i(B 1)=i(B 2) for all real symmetric matrices B 1,B 2∈Q(A).The purpose of this paper is to characterize double star and cycle sign patterns that require unique inertia. Further,their unique inertia is also obtained.
文摘A sign pattern(matrix)is a matrix whose entries are the symbols+,-and 0.Foran n×n sign pattern matrix A,the sign pattern class of A,denoted by Q(A),is the set ofall n×n real matrices whose entries have signs indicated by the corresponding entries of A.We say that a sign pattern matrix A requires a matrix property P if every real matrix in Q(A)has the property P.A matrix with all distinct eigenvalues has many nice
文摘In qualitative and combinatorial matrix theory,we study properties of a matrix basedon qualitative information,such as the signs of entries in the matrix.A matrix whose en-tries are from the set{+,-,0}is called a sign pattern matrix (or sign pattern).For a re-al matrix B,by sgn (B) we mean the sign pattern matrix in which each positive (respec-tively,negative,zero) entry of B is replaced by+(respectively,-,0).If A is an
文摘Let P be a property referring to a real matrix. For a sign pattern A, if there exists a real matrix B in the qualitative class of A such that B has property P, then we say A allows P. Three cases that A allows an M matrix, an inverse M matrix and a P 0 matrix are considered. The complete characterizations are obtained.
基金Supported by the Research Project of Leshan Normal University (LZD016, DGZZ202023)。
文摘Finding the necessary and sufficient conditions for a sign pattern to allow diagonalizability is an open problem. In this paper,we identify sign patterns of up to four orders that allow diagonalizability.
基金Supported by Shanxi Province Science Foundation for Youths(Grant No.201901D211227).
文摘Let S be a nonempty, proper subset of all possible refined inertias of real matrices of order n. The set S is a critical set of refined inertias for irreducible sign patterns of order n,if for each n × n irreducible sign pattern A, the condition S ? ri(A) is sufficient for A to be refined inertially arbitrary. If no proper subset of S is a critical set of refined inertias, then S is a minimal critical set of refined inertias for irreducible sign patterns of order n.All minimal critical sets of refined inertias for full sign patterns of order 3 have been identified in [Wei GAO, Zhongshan LI, Lihua ZHANG, The minimal critical sets of refined inertias for 3×3 full sign patterns, Linear Algebra Appl. 458(2014), 183–196]. In this paper, the minimal critical sets of refined inertias for irreducible sign patterns of order 3 are identified.
基金The NSF(10871188)of Chinathe NSF(KB2007030)of Jiangsu Provincethe NSF(07KJD110702)of University In Jiangsu Province.
文摘For a symmetric sign pattern S1 the inertia set of S is defined to be the set of all ordered triples si（S） = {i（A） ： A = A^T ∈ Q（S）} Consider the n × n sign pattern Sn, where Sn is the pattern with zero entry （i,j） for 1 ≤ i = j ≤ n or｜i -j｜=n- 1 and positive entry otherwise. In this paper, it is proved that si（Sn） = {（n1, n2, n - n1 - n2）｜n1≥ 1 and n2 ≥ 2} for n ≥ 4.
基金National Natural Science Foundation of China(Grant No.11071227)Shanxi Scholarship Councilof China(Grant No.12-070)
文摘An n × n complex sign pattern （ray pattern） S is said to be spectrally arbitrary if for every monic nth degree polynomial f（λ） with coefficients from C, there is a complex matrix in the complex sign pattern class （ray pattern class） of 3 such that its characteristic polynomial is f（λ）. We derive the Nilpotent-Centralizer methods for spectrally arbitrary complex sign patterns and ray patterns, respectively. We find that the Nilpotent-Centralizer methods for three kinds of patterns （sign pattern, complex sign pattern, ray pattern） are the same in form.
文摘Let A be a real matrix or a sign pattern of order n. N_-(A) denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A~2≤0, then (N_-(A~2)≤)(n-1)~2+1. Now the conjecture is proved to be true when A is reducible or a matrix of order n≤3 and some sufficient conditions for N_-(A~2)≤(n-1)~2+1 are given. It is also proved that N_-(A~2)≤n~2-(4n+)5 when A is a reducible combinatorially symmetric sign pattern such that A~2≤0, and the extreme sign patterns are characterized.
基金the Shanxi Natural Science Foundation (20011006, 20041010)
文摘A sign pattern is a matrix whose entries axe from the set {＋,-,0}. A sign pattern is a generalized star sign pattern if it is combinatorial symmetric and its graph is a generalized star graph. The purpose of this paper is to obtain the bound of minimal rank of any generalized star sign pattern （possibly with nonzero diagonal entries）.
基金Supported by Shanxi Natural Science Foundation(20011006)
文摘A matrix whose entries are +,-, and 0 is called a sign pattern matrix. Let k be arbitrary positive integer. We first characterize sign patterns A such that .Ak≤0. Further, we determine the maximum number of negative entries that can occur in A whenever Ak≤0. Finally, we give a necessity and sufficiency condition for A2≤0.
文摘Assume that S is an nth-order complex sign pattern.If for every nth degree complex coefficient polynomial f(λ)with a leading coefficient of 1,there exists a complex matrix C∈Q(S)such that the characteristic polynomial of C is f(λ),then S is called a spectrally arbitrary complex sign pattern.That is,if the spectrum of nth-order complex sign pattern S is a set comprised of all spectra of nth-order complex matrices,then S is called a spectrally arbitrary complex sign pattern.This paper presents a class of spectrally arbitrary complex sign pattern with only 3n nonzero elements by adopting the method of Schur complement and row reduction.
基金Foundation item： the National Natural Science Foundation of China （No. 10571163） the Natural Science Foundation of Shanxi Province （No. 20041010 2007011017）.
文摘If every monic real polynomial of degree n can be achieved as the characteristic polynomial of some matrix B∈Q(A),then sign pattern A of order n is a spectrally arbitrary pattern.A sign pattern A is minimally spectrally arbitrary if it is spectrally arbitrary but is not spectrally arbitrary if any nonzero entry(or entries)of A is replaced by zero.In this article,we give some new sign patterns which are minimally spectrally arbitrary for order n≥9.
