NIU Department of Mathematical Sciences
Research interests of the faculty

Here are brief statements from our faculty about their current research. You also can find out their research interests from Math Review


GREG AMMAR (Professor) – Ph.D., Case Western Reserve University. Numerical Linear Algebra, Scientific Computation, Numerical Methods in Signals, Systems, and Control.

My research activities are primarily in numerical linear algebra and scientific computation, with focus on algorithms for problems involving structured matrices that find applications in signal processing and control engineering. The structured problems that I have worked on include:

Additional information and copies of some recent papers can be found on the publication list on my home page.


HAMID BELLOUT (Professor) – Ph.D., Purdue University. Partial Differential Equations.

I am interested in the qualitative behavior of solutions to non-linear partial differential equations, more particularly in establishing the existence of singular solutions and providing a precise description of the singularities.

My main interest is in parabolic and elliptic equations with secondary interest in hyperbolic equations. Recently I have been focusing on mathematical problems arising from fluid mechanics.

Selected Publications:

  1. Stability result for the inverse transmissivity problem. Journal of Math Analysis and Applications, vol. 168, 1992, 13-27.
  2. Phenomenological Behavior of Multipolar Viscous Fluids. (with F. Bloom and J. Necas). Quarterly of Applied Mathematics, vol. L, number 3, 1992, 559-583.
  3. On some singular solutions of the equation $\DELTA u = -\lambda eu$. Commun. in Partial Differential Equations, 15(4), 525-539(1990).

JAMES BENSON (Assistant Professor) – Ph.D., University of Missouri. Mathematical Biology.

I am a mathematical biologist focusing on cryobiology, the study of life at low temperatures. Cryobiology presents a natural setting for mathematical problems involving heat and mass transfer in biological systems, often coupled to external environments. My contributions involve parameter identification, model formulation, and optimization of these models.

My current research is on the analytic and numeric optimal control of the heat and mass transfer problems intrinsic to cryobiology. I am also involved with the construction of thermodynamically accurate (and thus nonlinear) models of the interaction between cells and tissues and highly non-ideal envirionments. These problems couple classic free-boundary problems from phase field theory with solution theory along with considerations generated by cell-media interactions.


HARVEY BLAU (Professor) – Ph.D., Yale University. Finite Group Theory.

My area has proceeded from the representation theory of finite groups to a more general field of algebraic combinatorics focused on algebras with a distinguished basis. These algebras are variously called hypergroups, character algebras, and table algebras, among other names. Applications range from geometric symmetry via group algebras to combinatorial symmetry via adjacency algebras of association schemes to symmetries of quantum physics via the fusion rings that underlie fusion categories. Some specific projects of mine have examined (1) the generalization of Sylow theory from finite groups to table algebras; (2) the classification of integral table algebras and association schemes that are generated by a basis element of small degree; (3) classification of integral table algebras from data on representation-theoretic invariants such as multiplicities; (4) decomposition of products in nilpotent table algebras, generalizing results for conjugacy classes and irreducible characters of nilpotent groups.

References:

  1. Sylow theory for table algebras, fusion rule algebras, and hypergroups, with P.-H. Zieschang, J. Algebra 273 (2004), 551-570.
  2. Integral table algebras and Bose-Mesner algebras with a faithful nonreal element of degree three, J. Algebra 231 (2000), 484-545.
  3. Association schemes, fusion rings, C-algebras, and reality-based algebras where all nontrivial multiplicities are equal, J. Algebraic Combin. 31 (2010), 491-499.
  4. Decomposition of products in nilpotent table algebras, J. Algebra 323 (2010), 1581-1592.
  5. Table algebras, European Journal of Combinatorics 30 (2009), 1426-1455.

RICHARD BLECKSMITH (Professor) – Ph.D., University of Arizona. Number Theory.

My specialty is computational number theory. Although I have stayed away (somewhat) from the well-worn path of primarily testing and factorization, I have used the computer to investigate several interesting combinatorial and number theoretic problems.

Over the last ten years I have worked with John Brillhart, from the University of Arizona and Irving Gerst, from S.U.N.Y. at Stony Brook (Prof. Gerst passed away in 1996) on infinite product identities, especially those involving the Jacobi triple product functions. These functions have very nice product and series representations. Although no one knows an easy way to tell the parity of the partition function, we have found two infinite classes of restricted partitions whose parity can be immediately determined. The three of us were funded by the N.S.F. for two years to study these functions via computer. Recently we have discovered combinatorial mappings we hope will lead to symbolic computer proofs and ultimately a classification of these interesting identities.

A few years ago Paul Erdos introduced the concept of d-completeness. A sequence of positive integers u1, u2, ... is said to be d-complete if every sufficiently large integer n can be represented as a sum of the ui with the condition that no summand divides another. The sequence {2a3b} is d-complete and it is the only such sequence of that form. Recently J. L. Selfridge and I settled one of Erdos' last conjectures concerning the growth of the smallest term needed in these representations. Selfridge and I were working on a joint project with Erdos involving cluster primes. These are prime numbers p with the property that every even number less than p-3 can be written as a difference of primes no larger than p itself. Computationally, the cluster primes appear to have the same density as the twin primes.


DOUGLAS BOWMAN (Professor) – Ph.D., UC Los Angeles. Combinatorics.

My research centers around using combinatorics and analysis for attacking problems in special functions and, in particular, number theory.

The topics which interest me most are continued fractions, multiple polylogarithms (and their special values), q-series, and orthogonal polynomials. I am also interested in some aspects of diophantine approximation.


BISWA NATH DATTA (Professor) – Ph.D., University of Ottawa. Numerical Analysis.

My research is interdisciplinary in nature, blending theoretical and applied and computational linear algebra with application areas such as control and systems theory.

The control theory is a major source of beautiful linear algebra problems. The design and analysis of linear control systems give rise to well-known linear algebra problems such as Eigenvalue and Eigen-Structure Assignment Problems, Frequency Response Problems, Controllability and Observability Problems, Matrix Equations Problems, Stability and Inertia Problems, etc. The development of numerically effective algorithms for these problems, especially algorithms for Large Problems and those suitable for implementation on existing vector and parallel machines are of utmost importance. Numerical algorithms for control problems are still in their infancy. The control theory is lagging behind in this respect compared to other areas of applied sciences and engineering. Yet, there are control problems which are so large that they can be termed as ``Super Computer Problems''. An outstanding example is that of Large Space Structures (LSS).

My current research centers around understanding and analysis of the existing algorithms and developing new numerically viable algorithms, both sequential and parallel, for linear algebra problems in control. A particular attention is being given to the development of algorithms for large-scale solutions of problems arising especially from second order differential equations associated with large space structure problems. In the design of parallel algorithms for control problems, we make use of the existing sophisticated parallel algorithms for matrix computations and the associated software libraries presently being built both for distributed and shared-memory computers such as CRAY XMP and Hypercubes. My research addresses the urgent need clearly pointed out in the recent NSF panel report on ``FUTURE DIRECTIONS IN CONTROL THEORY.''


PAUL DAWKINS (Assistant Professor) – PhD, The University of Texas at Arlington. Mathematics Education.

My research focuses on Mathematics teaching and learning at the undergraduate level. My previous studies investigated problem solving among calculus students and the development of defining and proving among advanced calculus (analysis) students.

I am particularly interested in the transition to advanced mathematical thinking, classroom communication, and the emergence of communal mathematical meaning.


SIEN DENG (Professor) – Ph.D., University of Washington. Optimization Theory, Nonsmooth Analysis, and Applied Functional Analysis.

My research interests are in optimization along with related areas of nonsmooth analysis. Currently I am working on


NADER EBRAHIMI (Professor) – Ph.D., Iowa State University. Statistics.

My main area of research is in Reliability and Life Testing. My recent interest is to model the lifetime of a system through several stochastic processes and use the model to estimate its reliability.


ALASTAIR FLETCHER (Assistant Professor) – Ph.D., University of Warwick. Complex Analysis.

My research can broadly be described as complex analysis with two main areas of study, both of which feature centrally the notion of quasiconformal mappings:

- Quasiregular dynamics is a natural generalization of the iteration theory of holomorphic mappings in the plane to higher dimensions. This is a relatively new area of research which shows plenty of promise in being fertile for years to come.

- Teichmueller theory is a beautiful subject bringing together complex analysis, topology, geometry and more to describe deformation spaces of surfaces. This is a deep, challenging subject.

Further details on my research and contributions to these areas can be found on my publications page here


MICHAEL GELINE (Assistant Professor) – PhD, The University of Chicago. Finite Group Theory.

I study representations of finite groups and am particularly interested in relationships between rationality questions and some classical conjectures in block theory such as Brauer's height zero conjecture, Brauer's k(B) conjecture, and McKay's conjecture.

These conjectures are usually studied in the context of particular families of simple or quasisimple groups (usually of Lie type). My approach differs substantially in that I attempt to draw as much as possible from the theory of vertices and sources. The techniques come down to integral representations of p-groups.


DAN GRUBB (Associate Professor) – Ph.D., Kansas State University. Harmonic Analysis.

I work in Abstract Harmonic Analysis. This involved the analysis of functions, measures, and related structures in the setting of locally compact groups. My work often involves substantial amounts of functional analysis, as well as topology.

My specific interests concern generalizing certain relatively well-known results from classical Fourier analysis to the setting of locally compact abelian groups.


BERNARD HARRIS (Professor) – Ph.D., University College, Cardiff. Differential Equations.

Ordinary differential equations and asymptotic analysis. In particular linear equations and questions relating to the spectral theory. I also work on questions involving the qualitative theory of ordinary differential equations.


K.L. HOLLAND (Associate Professor) – Ph.D., University of Illinois at Chicago. Model Theory.

Professor Holland's research interests are in model theory, a branch of mathematical logic. She is particularly interested in the study of strongly minimal theories through their associated combinatorial geometries. Her recent work has centered on fusion, a means of constructing new strongly minimal sets from known ones.


YOOPYO HONG (Associate Professor) – Ph.D., The Johns Hopkins University. Matrix Analysis.

My research interest is in complex matrices. Currently, I am working on the properties of nonsingular matrices under $\Phi$-maps, i.e., equivalences, canonical form, invariances, spectral structures, generalized singular or polar decomposition under a $\Phi$-map, and so on, Rank revealing QR factorization, and other problems in (numerical) matrix theory.

Recent Publications:

  1. A characterization of unitary congruence, Linear and Multilinear Algebra, 25 (1989), 105-119.
  2. The Jordan Canonical form of a product of a Hermitian and a positive semidefinite matrix (to appear, Linear Algebra and its Applications).
  3. A canonical form under $\phi$-equivalence (to appear, Linear Algebra and its Applications).

BALAKRISHNA HOSMANE (Associate Professor) – Ph.D., University of Kentucky. Categorical Data Analysis, Linear and Nonlinear Mixed Models, Pharmaceutical Statistics.

The statistical methodology is being developed to assess the non-inferiority testing of ECG parameters in both cross-over trials and parallel studies with baseline covariates. This methodology is applied to study the safety of every new chemical entity (new drug) that is being developed by pharmaceutical industry.

1. A Simulation Study of Power in 'Thorough' QT/QTc Studies and a Normal Approximation for Planning Purposes (with Charles Locke), Drug Information Journal. 2005.

2. Using lower trophic level factors to predict outcomes in classical biological control of insect pests (with Gross, et. al), Basic and Applied Ecology. 2005.

3. Test for misspecification of link in dependent binary regression using generalized estimating equations (with Calachan-Molefe), Journal of Statistical Computation and Simulation. 2005.


LEI HUA (Assistant Professor) – Ph.D., University of British Columbia. Statistics.

My research interests are motivated by applications. My recent research emphasis has been on the tail behavior of multivariate non-Gaussian phenomena and its influence on risk measures. The former incorporates the tail behavior of margins (e.g., tail heaviness and skewness) and the limiting properties of their dependence structures (e.g., tail dependence and asymptotic independence); the latter concerns issues that are meaningful to finance and insurance. In addition to applications in insurance and finance, the study of multivariate non-Gaussian phenomena is beneficial to other research fields, such as environmetrics and network data analysis.


HELEN A. KHOURY (Associate Professor) – Ph.D., Florida State University. Mathematics Education.

The focus of my mathematics education research has been on investigating students' mathematical learning with the intention of attempting to improve mathematical instruction. In specific, my research emphasis has been on understanding students' intellectual and constructive mathematical development. I have worked with students, in groups and individually, and I have observed and analyzed the reasoning strategies students apply in specific mathematical problem-solving situations, as well as the connections they form with their mathematical and othe domains of knowledge.

In my research, I have investigated the mathematical reasoning strategies which students use as they solve problems related to any of the following multiplicative-structured concepts: place-value, rational numbers and proportions, equation-solving, functions, probability, correlations, and conditional logic. I have worked with students of various ages: elementary school students, secondary school students, and college level students including preservice school teachers. In my research, I have applied both quantitative and qualitative research methodologies depending upon the questions that were investigated. Currently, along with the identification and analyses of students' developmental reasoning and problem-solving strategies, I am also investigating students' structures of conceptual units and their flexibility of reasoning during problem solving.


ILYA KRISHTAL (Associate Professor) – Ph.D., Voronezh State University, Russia . Harmonic Analysis & Operator Theory.

My research interests cover a wide range that includes spectral theory of linear operators and linear relations as well as abstract and applied harmonic analysis. I am investigating problems in frame theory, wavelet and time-frequency analysis, sampling theory, causal pseudo-differential operators, etc. A usually up-to-date list of my publications and preprints is available on my home page.


NATHAN KRISLOCK (Assistant Professor) – Ph.D., University of Waterloo. Numerical Optimization.

My research is in the area of continuous and combinatorial optimization with a focus on:

- convex analysis; semidefinite optimization; semidefinite relaxations of hard combinatorial problems;

- sparse and low-rank optimization, matrix completion, and matrix approximation (least-squares) problems;

- Euclidean distance matrices and applications:

    - wireless sensor network localization;

    - protein structure determination;

- numerical optimization and linear algebra; large-scale computation.


QINGKAI KONG (Professor) – Ph.D., University of Alberta. Differential Equations.

My research interests are mainly in the qualitative analysis of differential equations and its applications which include:


Y. C. KWONG (Associate Professor) – Ph.D., University of Wisconsin. Partial Differential Equations.

My field of research is in Non-linear Partial Differential Equations. It can be mainly divided into 2 parts:

References:


RAMA T. LINGHAM (Associate Professor) – Ph.D., Purdue University. Statistics.

My main area of research is Bayesian Statistical Inference from Stochastic Processes. I also have research interest in Statistical Computing and Actuarial Modeling. Currently, Bayesian estimation, hypotheses testing and model selection issues relating to random processes are being pursued.

References:

  1. Intrinsic Bayes factor approach to a test about the Power Law process (with Dr. S. Sivaganesan), J. Statist. Planning Inf., vol. 77, 195-220, 1999.
  2. Bayes factors for a test about the drift of the Brownian motion under non-informative priors (with Dr. S. Sivaganesan), Statist. Probab. Lett., vol. 48, 163-171, 2000.
  3. On the Asymptotic Stability of the Intrinsic and Fractional Bayes Factors for Testing Some Diffusion Models (with Dr. S. Sivaganesan), Ann. Inst. Statist. Math, Vol. 54, No. 3, 500-516, 2002.
  4. Bayesian estimation of system reliability in Brownian stress-strength models (with Dr. Sanjib Basu), Ann. Inst. Statist. Math, Vol. 55, No. 1, 7-19, 2003

ANDERS LINNER (Associate Professor) – Ph.D., Case Western Reserve University. Differential Geometry and Global Analysis.

My current research interests are related to problems regarding periodic extremals. Many lasting non-chaotic physical phenomena can be viewed as extremals of this kind. By the use of essentially infinite dimensional methods it is possible to represent all periodic functions as a nonflat subset of the space of all functions. The extremals appear at points where the projected gradient vector field vanishes. In order to find these elusive extremals one attempts to follow the trajectories of the gradient vector field.

My methods have proven to be very useful when applied to so-called nonlinear splines in approximation theory. The techniques used involve differential geometry, global analysis, calculus of variations and optimal control. I also use Sobolev spaces, convexity, tensor analysis, numerical analysis, Mathematica, the C-language, computer graphics (real time and animated) and occasionally theories of physics. In the future some of this work will lead to computer implementations of new algorithms.

A good reference is my paper ``Curve straightening'' which appeared in ``Proceedings of Symposia in Pure Mathematics'' by the American Mathematical Society. This volume covers the AMS summer research institute in differential geometry at UCLA and it gives the state of the art as of 1990.


TAO LU (Assistant Professor) – PhD, University. Statistics


MAYA MINCHEVA (Assistant Professor) – PhD, University of Waterloo. Differential Equations applied to Biology.

Applications of systems of differential equations (ordinary, reaction- diffusion or delay) to (bio)chemical reaction network models. Specifically we analyze the connection between the structure of a biochemical network and its biological properties, such as multistability and oscillations. Also, we study the influence of space diffusion or time delays on the capacity of a biochemical network for multistability or oscillations.

Representative publications:

M.Mincheva, G. Craciun, Multigraph conditions for multistability, oscillations and pattern formation in biochemical reaction networks, Proc. of the IEEE 96, 1281-1291, 2008.

M. Mincheva, M. Roussel, Graph-theoretic methods for the analysis of chemical and biochemical networks. I. Multistability and oscillations in mass-action kinetics models, J. Math. Biol. 55, 61-86, 2007.

M. Mincheva, M. Roussel, Graph-theoretic methods for the analysis of chemical and biochemical networks. II. Oscillations in networks with delays, J. Math. Biol. 55, 87-104, 2007.

M. Mincheva, M. Roussel, A graph-theoretic method for detecting Turing bifurcations, J. Chem. Phys. 125, 204102, 2006.


DEEPAK NAIDU (Assistant Professor) – Ph.D., University of New Hampshire. Algebra and Representation Theory.

My research interests include tensor categories and Hopf algebras. I also study the structure of algebras, specifically their Hochschild cohomology and their associated deformations.


ALAN M. POLANSKY (Associate Professor) – Ph.D., Southern Methodist University. Nonparametric Statistics.

My research interests are in the general area of nonparametric Statistics. Specifically, my research focuses on the following areas:


ALON REGEV (Assistant Professor) – PhD, University of California, San Diego. Ring Theory.

My research generally deals with noncommuatative rings, and more specifically noncommutative infinite-dimensional algebras. I have studied the properties of nilpotent and algebraic elements in these algebras, in particular when the algebra is graded and when the base field is uncountable.


MARY SHAFER (Associate Professor) – Ph.D., University of Wisconsin. Mathematics Education.

Professor Shafer's current research in mathematics education is studying the impact of the Master of Science in Teaching specialization in Middle School Mathematics Education on teachers' knowledge of mathematics, teaching practices, and professional growth and the impact on their students' mathematics achievement and mathematical dispositions. This research is supported by the Mathematics and Science Partnership grant Excellence in the Middle: Enhancing Mathematics Pedagogy with Connections in Science and Engineering, funded by U.S. Department of Education, NCLB, Title II, Part B, through the Illinois State Board of Education. Professors Shafer and Khoury are co-directors of this grant, which is currently supporting 32 teachers from several high-needs Illinois school districts to complete graduate coursework toward the Master of Science in Teaching specialization in Middle School Mathematics Education. Professor Shafer co-authored a book with Thomas Romberg entitled The Impact of Reform Mathematics Instruction on Student Achievement: An Example of Standards-Based Curriculum Research, which was published in 2008. Her other publications have focused on teachers' pedagogical decisions and classroom assessment practices.


PENG SHI (Assistant Professor) – PhD, University of Wisconsin. Actuarial Science and Risk Management

My reseach involves using advanced statistical models in actuarial science, risk management and insurance. Particularly I am interested in longitudinal data analysis, copula regression and predictive modeling. The main current work are on multivariate stochastic loss reserving and testing asymmetric informance in insurance market.

Selected Publications:

Shi, P. and Frees, E.W. (2010). Long-tail longitudinal modeling of insurance company expenses, Insurance: Mathematics and Economics, 47(3), pp. 303-314.

Frees, E.W., Shi, P., and Valdez, E.A. (2009). Actuarial applications of a hierarchical insurance claims model, ASTIN Bulletin, 39(1), pp. 165-197. This article was awarded the Hachemeister Prize by Casualty Actuarial Society, 2010.


GLEB SIROTKIN (Associate Professor) – Ph.D., Indiana University-Purde University University Indianapolis. Functional Analysis.

I am interested in the following areas of Functional analysis and Operator theory.

* Geometry of Banach spaces (Hereditarily Indecomposable Banach spaces; Operators with and without invariant subspaces; Daugavet equation);

* Positive operators in Banach lattices (Invariant subspace problem for positive operators; Compact-friendly operators).


J. B. STEPHEN (Associate Professor) – Ph.D., University of Nebraska. Semigroups, Automata and Languages.

Present activity:


JEFF THUNDER (Professor) – Ph.D., University of Colorado. Number Theory.

My research interests are in Diophantine equations, Diophantine approximation, arithmetic geometry, and the geometry of numbers. The study of Diophantine equations deals with finding integral or rational solutions to polynomial equations. This is closely related to Diophantine approximation, where one studies approximations to real numbers by rational numbers. Arithmetic geometry, broadly speaking, deals with arithmetic properties (i.e., properties concerning the integers) of geometric objects, usually affine or projective varieties. This is an area where number theory and algebraic geometry come together. The geometry of numbers deals with points with integer coordinates in regions of real n-space (under what condition will a region have such a point? how many? etc...), sphere packing, and related subjects.



JOHN WOLFSKILL (Associate Professor) – Ph.D., California Institute of Technology. Number Theory.

I work mainly in algebraic number theory at a relatively elementary level, dealing with problems of classnumbers and units in algebraic number fields. I also make an occasional sideline into diphantine equations, that is, equations in which integer solutions are required. Some recent references are the following:


ZHUAN YE (Professor) – Ph.D., Purdue University. Complex Analysis.

Motivated by P. Vojta's dictionary of number-theory-Nevanlinna-theory and related S. Lang's questions, my current research interests are finding analogies of Diophantine approximation in Nevanlinna theory of meromorphic mappings between two complex manifolds.


ALAN ZOLLMAN (Associate Professor) – Ph.D., Indiana University. Mathematics Education.

My scholarship focuses on research-based, classroom-tested curriculum innovations and implementation implications in science, technology, engineering, and mathematics (STEM) education. Research investigations are in the areas of reflective abstraction and teacher beliefs.


Last modified: 9/10/2012 by gradprog@math.niu.edu