# Mathematics & Statistics Faculty

• Professor
• Professor

## Recent Submissions

• (Elsevier, 2015-08-15)
The enhanced principal rank characteristic sequence (epr-sequence) was originally defined for an n ×n real symmetric matrix or an n ×n Hermitian matrix. Such a sequence is defined to be l1l2···ln where lk is A,S, or N ...
• (Elsevier, 2015)
The positive semidefinite zero forcing number of a graph is a graph parameter that arises from a non-traditional type of graph colouring and is related to a more conventional version of zero forcing. We establish a relation ...
• (Wiley Periodicals, Inc., 2013)
Tree-width, and variants that restrict the allowable tree decompositions, play an important role in the study of graph algorithms and have application to computer science. The zero forcing number is used to study the ...
• (2014)
The zero forcing number and the positive zero forcing number of a graph are two graph parameters that arise from two types of graph colourings. The zero forcing number is an upper bound on the minimum number of induced ...
• (Elsevier, 2014)
Given an n-by-n matrix, its principal rank characteristic sequence is a sequence of length n + 1 of 0s and 1s where, for k = 0; 1,..., n, a 1 in the kth position indicates the existence of a principal submatrix of rank ...
• (Elsevier, 2015)
The enhanced principal rank characteristic sequence (epr-sequence) of a symmetric n ×n matrix is a sequence from A,S, or N according as all, some, or none of its principal minors of order k are nonzero. Such sequences give ...
• (The Charles Babbage Research Centre, 2013-02)
In this work, we study the structure of the null spaces of matrices associated with graphs. Our primary tool is utilizing Schur complements based on certain collections of independent vertices. This idea is applied in ...
• (International Linear Algebra Society, 2013-01)
The Colin de Verdi`ere parameters mu and nu are defined to be the maximum nullity of certain real symmetric matrices associated with a given graph. In this work, both of these parameters are calculated for all chordal ...
• (International Linear Algebra Society, 2013-09)
The minimum number of distinct eigenvalues, taken over all real symmetric matrices compatible with a given graph G, is denoted by q(G). Using other parameters related to G, bounds for q(G) are proven and then applied to ...
• (Public Knowledge Network, 2013)
We establish the bounds 4 on the Nordhaus- Gaddum sum upper bound multipliers for all graphs G, in connections with certain Colin de Verdi ere type graph parameters. The Nordhaus-Gaddum sum lower bound is conjectured ...
• (International Linear Algebra Society, 2014-06)
Barrett et al. asked in [W. Barrett et al. Minimum rank of edge subdivisions of graphs. Electronic Journal of Linear Algebra, 18:530–563, 2009.], whether the maximum nullity is equal to the zero forcing number for all ...
• (Elsevier, 2008)
The fixed-point iteration is a simple method for finding the maximal Hermitian positive definite solutions of the matrix equations $X\pm A^*X^{-1}A=I$ (the plus/minus equations). The convergence of this method ...
• (SIAM, 2009)
Hyperbolic quadratic matrix polynomials $Q(\lambda) = \lambda^2 A + \lambda B + C$ are an important class of Hermitian matrix polynomials with real eigenvalues, among which the overdamped quadratics are those with ...
• (SIAM, 2009)
In this paper, we review two types of doubling algorithm and some techniques for analyzing them. We then use the techniques to study the doubling algorithm for three different nonlinear matrix equations in the critical ...
• (SIAM, 2009)
A 25-year old and somewhat neglected algorithm of Crawford and Moon attempts to determine whether a given Hermitian matrix pair $(A,B)$ is definite by exploring the range of the function $f(x) = x^*(A + iB)x/|x^*(A + ... • (Elsevier, 2010) If$A$is a matrix with no negative real eigenvalues and all zero eigenvalues of$A$are semisimple, the principal$p$th root of$A$can be computed by Newton's method or Halley's method, with a preprocessing procedure ... • (Elsevier, 2010) We determine and compare the convergence rates of various fixed-point iterations for finding the minimal positive solution of a class of nonsymmetric algebraic Riccati equations arising in transport theory. • (SIAM, 2010) The matrix equation$X+A^TX^{-1}A=Q$has been studied extensively when$A$and$Q$are real square matrices and$Q$is symmetric positive definite. The equation has positive definite solutions under suitable conditions, ... • (SIAM, 2010) In studying the vibration of fast trains, we encounter a palindromic quadratic eigenvalue problem (QEP)$(\lambda^2 A^T + \lambda Q + A)z = 0$, where$A, Q \in \mathbb{C}^{n \times n}$and$Q^T = Q$. Moreover, the matrix ... • (Elsevier, 2011) We study the matrix equation$X+A^{T}X^{-1}A=Q$, where$A$is a complex square matrix and$Q\$ is complex symmetric. Special cases of this equation appear in Green's function calculation in nano research and also in the ...