# The Hudson Colloquium Series

In 1988, at the initiative of Dr. Anne Hudson, the then Department of Mathematics and Computer Science at Armstrong State College began a near-weekly luncheon colloquium. Students and faculty would gather in the luxurious confines of Hawes 203 for hot dogs, spaghetti, taco salad, etc., and an enjoyable talk on some topic in mathematics or computer science. In 2003 this luncheon-colloquium series was named in honor of Anne and Sigmund Hudson.

Today, the colloquium is sponsored by the Department of Mathematics and takes place on Wednesdays at 12:15pm in University Hall, room 157 (unless otherwise noted). For a donation of a dollar—$2 for faculty and other non-students—you can enjoy a delicious light lunch, invigorating conversation with students and faculty members, and a lecture, demonstration, or other event arranged by faculty, students and/or visitors. Please come. Please contact Dr. Tricia Brown if you are interested in giving a presentation. Also, please send your email address to Dr. Brown if you would like to be added to the mailing list. If you're interested in helping with lunch preparation, please contact Dr. Brown. Her email is Patricia.Brown@armstrong.edu ## Spring 2012 April 6 Jim Coykendall, North Dakota State University A Tour of Factorization Abstract: Factorization is one of the first concepts that any person encounters in their mathematical journey. Although factorization is a familiar concept, it can be quite deep and mysterious; sometimes it baffles the intuition. Throughout the past 20 years or so, the concept of factorization in integral domains has become a rich and vibrant area of study in algebra. The aim of this talk is to give an overview of modern factorization theory from an example-oriented point of view. We will not be heavy-handed with respect to rigor, but rather, try to give the audience a general intuitive feel for the questions and results that motivate this area of research. And many examples will be given to shine light on the beauty and elegance of the structure of factorization. March 21 James Brawner, Sungkon Chang, Joshua Ferrerra Reflections on the 72th Annual Putnam Mathematical Competition Abstract: In December 3, 2011, an intrepid team of Armstrong students spent most of their Saturday working on a dozen frighteningly challenging mathematical problems. Why? Just another installment of the notoriously difficult William Lowell Putnam Mathematical Competition. Members of the team and faculty members will discuss solutions of their favorite problems from the most recent competition. March 7 Dr. Joshua Cooper, University of South Carolina The Minimum Number of Givens in a Fair Sudoku Puzzle is 17 Abstract: Add one more reason to love the number 17*. McGuire, Tugeman, and Civario surprised many in the mathematics-of-Sudoku community on January 1, 2012 by posting the result of a huge computation apparently confirming the long-held suspicion that the fewest number of givens in a fair Sudoku puzzle is 17. The proof is a combination of clever programming techniques, mathematical analysis of so-called "hitting sets", and a massive supercomputer computation. We discuss how they did it, what it means, and where to go from here. * Just for some purely mathematical examples: 17 is a twin prime, a Mersenne prime exponent, an Eisenstein prime, a Fermat prime, the number of wallpaper (plane isometry) groups, the length of the longest Berlekamp-Graham "perfectly distributed" sequence in [0,1], the least nontrivial hexadecimal repunit prime, the number of orthogonal curvilinear coordinate systems up to conformal symmetry for which the 3-variable Laplace equation can be solved using separation of variables, and the least number that can be written as the sum of a positive cube and a positive square in two different ways. February 22 Dr. Michael Tiemeyer Cycle Frames of Multipartite Graphs Abstract: Let M(b,n) be the complete multipartite graph with b parts of size n. A z-cycle system of M(b,n) is said to be a cycle-frame if the z-cycles can be partitioned into sets such that each set induces a 2-factor of M(b,n) minus some part. The existence of a z-cycle-frame of M(b,n) has been settled when z = {3,4}. Here, we consider z-cycle-frames when z>4 is even. February 8 Dr. Travis Trentham Purgatory Domains Abstract: We begin by recalling that an irreducible x in an integral domain D is any nonzero nonunit of D that cannot be expressed as a product of more than one nonunit of D. For example, every prime integer is irreducible in the ring of integers. Sometimes irreducibles are also called atoms. If every nonzero nonunit of our domain D can be expressed as a product of atoms, then we say D is atomic. Every UFD and every Noetherian domain is atomic. Examples abound of (non-field) domains that contain no atoms at all. These rings are called antimatter domains and it can be argued that they constitute the worst of all possible worlds from a factorization point of view. However, there is a class of domains which form a middle ground in that they contain atoms but also have elements which do not admit atomic factorizations. Such a ring is called a Purgatory domain. Hence, every domain is either atomic, an antimatter domain, or lies in Purgatory. We will consider examples of these rings and demonstrate how the isomorphism class of any domain can be uniquely associated to the isomorphism class of a Purgatory domain. Hence, if there is a largest class among these three types of domains, it must be the Purgatory class. January 20 Dr. Yan Wu, Georgia Southern University Stability Analysis of Adaptive Control of SIngle-Loop Thermosyphon via Wavelet Network Abstract Compactly supported orthogonal wavelets have certain properties that are useful for controller design. A wavelet network serves as a universal approximant for functions in L^2(R^n) in such as a nonlinear state feedback controller. The mechanism of a wavelet controller is revealed via integration with linear time-invariant systems. We obtain closed-form bounds on the design parameters of a wavelet controller which guarantee asymptotic stability of the wavelet-controlled LTI systems. We further investigate global stability of wavelet-controlled nonlinear dynamical systems, such as a loop thermosyphon, in which the nonlinearity of the system is approximated so that a classical proportional state feedback control is sufficient for stabilizing the chaotic flow in the thermosyphon. ## Fall 2011 November 16 Sungkon Chang Introduction to Differential Geometry Abstract: This talk is the ?rst part of my presentation for Differential Geometry and General Relativity, and the second part will be given in Spring 2012. Differential Geometry was rapidly developed around 1800 by great mathematicians such as Gauss, Riemann, and Poincaré, and became the source of modern mathematical subjects such as Lie/Representation theory, Algebraic Topology, and Algebraic Geometry. As the ideas in all these purely abstract mathematical subjects were used in modern physics, Differential Geometry serves as a subject in the undergraduate curriculum by which both math and non-math major undergraduate students may appreciate pure mathematics and the practicality of the art of mathematical thinking. Fully understanding this talk requires Calculus 3 and linear algebra, but as the subject directly appeals to our geometric intuition, I would like to invite all students who are interested. November 2 Lorrie Hoffman Best estimators in broken-line regression Abstract: Assuming cause and effect for physical phenomena leads scientists to expect that all data sets are generated by some underlying model. In simple models the effect (outcome, say y(t), called the dependent, predicted or response variable) is linearly related to the cause (perhaps, time t, called the independent or predictor variable). Regression analysis is a statistical technique used to compute parameters of underlying models. Depending on the definition of “best”, we can generate different estimators (formulas/functions) by conducting a regression analysis. Parameters of the model are estimated by these statistics/estimators as functions of the data. Certain properties such as unbiasedness and minimum variance are considered strong indicators of the “goodness” of the estimators. We will define and explore some of these properties when assessing various estimators in the single line model case. We will briefly discuss extending the investigation to estimators under the broken-line regression scenario, the case where there are two lines, one consisting of a trend line and the other a horizontal ray that meet at a joinpoint. This work is theoretical in nature and mirrors the assessment efforts via simulation undertaken in the paper by Hoffman, Knofczynski and Clark (2010). October 14 Mark Budden, Western Carolina University Paley graphs Inspired by Paley's use of the Legendre symbol to construct Hadamard matrices, Sachs first defined Paley graphs in 1962. Such graphs have vertices identified with the elements of a finite field$\mathbb{F}_q$, where$q\equiv 1\pmod{4}$is a power of a prime, and an edge connects vertices$a$and$b$if and only if$b-a\in \mathbb{F}_q ^{\times 2}$, the subgroup of squares in the multiplicative group$\mathbb{F}_q ^{\times}$. In this talk, we will consider a generalization of Paley graphs known as character difference (di)graphs and will investigate some of their basic properties. In particular, we find that many problems involving adjacency in such (di)graphs may be solved through the tedious evaluation of character sums in number theory. Furthermore, many classical number theoretic problems (such as finding the size of maximal difference sets of quadratic residues) may be approached by studying the properties of such (di)graphs. October 4 Tricia Muldoon Brown The Robinson-Schensted Algorithm Abstract: We introduce two familiar combinatorial objects, partitions and permutations, and give a bijection between sets of these objects. An algorithm due to Robinson and Schensted that makes use of another combinatorial object, Young diagrams, defines this bijection. The talk concludes with some questions. September 21 Travis Trentham The Axiom of Choice Abstract: In this discussion we will be looking at the Axiom of Choice and some of the statements which are equivalent to it. In particular, we will be looking at Zorn's Lemma and the Well-Ordering Principle as well as some applications of all three. These applications will highlight not only the utility of the Axiom but also how it tends to keep popping up in a surprisingly broad spectrum of mathematical disciplines. Additionally, we will look at how the Axiom arises in a way that makes its usage seem both inevitable and necessary. However, there are a number of remarkable (some would say "disturbing") consequences of its usage, which we will be looking at that might make you want to completely reject its veracity. This discussion will be example-heavy and should quite accessible to an undergraduate audience. September 7 Jim Brawner Folding Graphs into Polyhedra Abstract: In the branch of mathematics called graph theory, a graph is a collection of dots, called vertices, some of which are connected by line segments or curves, called edges. In this talk we will explore the question of which graphs can be folded, by gluing together various vertices, and perhaps stretching edges as needed, into three-dimensional frames of particular polyhedra. To whet your appetite, can you see how you might fold the bug-shaped graph on the left into a cube? How about the “hexastar” graph on the right? Can you also fold the hexastar graph into an octahedron? The talk will focus on finding graphs that can be folded into two different polyhedra. ## Spring 2011 April 20 Lorrie Hoffman A Non-Least-Squares Method For Estimation of Broken-line Regression to Determine Plateau Time of Outputs In Some Animal Science Studies Abstract: Broken-line regression has been used to estimate parameters in increasing or decreasing linear trends that later plateau. Most approaches employ least squares methods that under usual assumptions lead to maximum likelihood estimates (Gill, 2004). In Hoffman, Knofczynski and Clark (2010) an estimation procedure called MMNPR is derived and simulation studies show that parameter estimates of the broken-line regression perform better than the MLEs in small sample situations when data is from distributions where error terms are ill-behaved. A review of applied science literature revealed many studies using broken-line regression. We note three animal studies that report parameters based on least squares approaches: 1) determining times of steady milk production in cows (Sahinler, 2009), 2) transport of urea in mice (Marini, Lee and Garlick, 2006) and 3) the maximum sustained effect of dietary copper on chicks (Robbins, Norton and Baker, 1979). We investigate the appropriateness of underlying assumptions concerning correlation and homoscedacity. We then revisit the analysis of the animal data using the MMPNR technique, discussing differences between parameter estimates based on least squares and those based on the MMNPR technique. April 6 Robin Wilke Generating Lattice Polygons With Specified Number of Interior Points Abstract: How many unique lattice polygons are there with three interior points? The answer is... God knows! Finding the number of nonisomorphic two-dimensional convex lattice polygons with a specified number of interior points i is surprisingly hard: the number of inequivalent polygons with i ≥ 2 is still an open problem. We propose a new way to construct a complete set of lattice inequivalent polygons for any i, based on the relative minimality or maximality of polygons instead of the number of sides, and demonstrate it for i = 1 and i = 2. The algorithm presented allows insight into which polygons can be generated from which other polygons, inducing a directed graph structure into any set of inequivalent polygons for a value of i. Some combinatorial properties of these graphs will also be discussed. Finally, we discuss applications to cryptography, the theory of modular forms, and several problems in computational geometry. March 23 Sungkon Chang and others Reflections on the 71th Annual Putnam Mathematical Competition Abstract: In December 4, 2010, an intrepid team of Armstrong students spent most of their Saturday working on a dozen frighteningly challenging mathematical problems. Why? Just another installment of the notoriously difficult William Lowell Putnam Mathematical Competition. Members of the team and faculty members will discuss solutions of their favorite problems from the most recent competition. March 2 Michael Tiemeyer Four-Cycle Frames of the Complete Multipartite Graph Abstract: PDF version February 9 (postponed from January 26) Joshua Lambert Exploring Rational Residue Graphs Abstract: During the early 1960's, Horst Sachs introduced Paley graphs to the world of mathematics. Paley graphs tie together graph theory and number theory. We shall explore the symmetry of these rational residue graphs alongside the calculation of the number of triangles and the number of edge-disjoint hamiltonian cycles. ## Fall 2010 November 10 William Trentham Krull Dimension Abstract: Krull dimension is a notion of central importance in commutative algebra. One can think of Krull dimension as a measure of "how high" one can continue to stack up prime ideals in a ring. In this sense, we get an idea as to the size of the ring. In Dr. Trentham's doctoral thesis, he presented a generalization of the idea of Krull dimension. This generalization allows us to assign a unique cardinal number to every commutative ring with identity. Thus, in the infinite dimensional case, we are able to say what the Krull dimension of a ring actually is instead of being cornered into referring to what it is not, i.e., finite. In this discussion we will consider Krull dimension in both its traditional sense as well as this generalization. We will also perform some computations using this generalization. October 27 Tricia Muldoon Brown The Partial n-Queens Problem Abstract: The n-queens problem asks: Given a positive integer n, can n non-attacking queens be placed on an n x n chessboard? This problem and and its extensions have been studied by mathematicians for over 200 years. In this talk we discuss the history and several of the variations of the n-queens problem. We focus on the problem of finding a maximum solution given a partial arrangement of k non-attacking queens and demonstrate a computer algorithm which solves the partial problem for small n. October 6 Sungkon Chang The Algebra of Grand Unified Theory Abstract: The Standard Model representation in particle physics describes the three forces: the strong force, the weak force, and the electromagnetic force via the actions of the Lie algebras of Lie groups. A grand unified theory (GUT) is an attempt to describe the three forces via the action of the Lie algebra of a simple Lie group, thereby offering an elegant unified mathematical description of the action of the three forces. In this talk, the mathematics behind SU(5)-GUT will be introduced. Although SU(5)-GUT is no longer accepted in physics, it is an excellent prototype of GUTs, from which one can see how modern algebra plays a role in some fundamental part of physics. September 15 Paul Hadavas The Power of Proofs Abstract: In this talk, we will see why we need mathematical proofs, and then discuss various proofs for one of the most popular theorems of all time. A bonus "proof without words" for another well-known theorem will also be included. September 1 Selwyn Hollis Building Dynamic Demonstrations with Mathematica Abstract: With Mathematica, a remarkably small amount of code can result in a small interactive application, or "demonstration," with a sophisticated user interface. This talk will focus on the basic ideas involved in building demonstrations, using a few elementary classroom topics as examples. ## Spring 2010 April 21 Sungkon Chang, William Nathan Hack, Selwyn Hollis, Scott King, Tim McMillan Reflections on the 70th Annual Putnam Mathematical Competition Abstract: On December 5, 2009, an intrepid team of four Armstrong students spent most of their Saturday working on a dozen frighteningly challenging mathematical problems. Why? Just another installment of the notoriously difficult William Lowell Putnam Mathematical Competition. Members of the team and faculty members will discuss solutions of their favorite problems from the most recent competition. April 7 Dr. Joshua K. Lambert Coloring Checkerboards Abstract: The squares of an m by n checkerboard are alternately colored black and red. Two squares are called neighbors if they belong to the same row or the same column and there is no square between them. It is conjectured that we can place coins on some of the red squares such that every black square neighbors an odd number of coins. We shall discuss how this checkerboard problem relates to the newly conceived concept in graph theory of modular chromatic numbers. March 24 Moshe Cohen, Louisiana State University Domino Tilings, Perfect Matchings on Graphs, and the Alexander Polynomial of a Knot Abstract: The goal of this talk is to investigate how well-understood problems in combinatorics interact with a polynomial from knot theory. Combinatorics (the art of counting) asks questions like "How many ways can we cover a checkerboard with dominoes?". A knot is a circle embedded in three dimensional space. Knot theory asks "How can we tell two knots apart?". The Alexander polynomial is one example of a knot invariant (that is, if the Alexander polynomials of two knots are not the same, the knots must be different). This polynomial is the determinant of a matrix, and we'll construct this matrix using techniques from combinatorics. March 3 Dr. Sabrina Hessinger Differential Galois Theory: An Area for Mathematicians Loving the Pure and the Applied! Abstract: In this talk we will introduce the basic constructs and ideas behind the field of Differential Algebra with a specific focus on Differential Galois Theory. This relatively young field of mathematics was formally developed by E.R. Kolchin et.al. in the mid 1970s. It involves differential equations, abstract algebra, computer algebra, linear algebra and topology. We’ll explore the various avenues of inquiry in differential Galios theory and discuss example results. February 10 Dr. Jared Schlieper Free, As In Beer Abstract: With all the talk of budget cuts, "free" has such a nice ring to it. In fact, there are many free open source programs that we can use to enhance our teaching. We will discuss using various open source mathematics software available and spend more time focused on two programs in particular: SAGE and WeBWorK. We will give a brief overview of each one along with classroom experiences from the past couple semesters. January 27 Dr. Patricia Brown How Deep Is Your Playbook? Abstract: Math Awareness Month is coming up in April and this year's theme is Math & Sports. In order to support MAM, this talk will include algebra, combinatorics, and football. We will discuss 4 basic defensive formations utilized in the National Football League and consider how many options a coach has when calling his play. No advanced knowledge of math (or football!) is necessary for this talk. ## Fall 2009 November 11 Dr. Mark Budden with Scott King and Alex Moisant Permutations of Rational Residues II Abstract: Reciprocity laws in number theory relate the residue symbols of distinct primes with one another. Mathematicians' attempts to extend such laws have guided the direction of algebraic number theory for hundreds of years and their results have implications throughout mathematics. In this talk, we will provide an overview of the natural setting for proving rational reciprocity laws and will explain how an extension of Zolotarev's 1872 proof of the Law of Quadratic Reciprocity may be generalized to proving more recent generalized rational laws. October 28 Dr. Jared Schlieper Financial Mathematics Abstract: Dr. Schlieper will take a brief excursion into financial math from the simple (interest) to the random. Financial mathematics has many topics that everyone will encounter at some point in their life (e.g., auto loans or mortgages). The area also includes stochastic models of interest rates and financial derivatives. Dr. Schlieper will go over a few examples to give an idea of the mathematics and statistics involved. (Disclaimer: The presenter takes no responsibility for your financial losses after the talk, but expects to be compensated for your gains.) October 7 Dr. Sungkon Chang The Equal Circle Packing Problem Abstract: For a closed convex region S in the Euclidean plane and a positive integer k, the equal circle packing problem is to find the largest radius a for which k open disks of radius a can be inscribed in S such that the disks do not intersect each other. This problem, which was introduced in the 1960's, is an interesting NP-hard optimization problem. With the aid of computer technology, the literature on computational results and algorithmic developments has been recently rich and active. This talk will introduce the theoretical aspects of the problem and will also introduce results for the six circle case. All students are invited, and especially those who are interested in research experience are encouraged to come and learn about the opportunity. September 2 Dr. Sean Eastman Using Numerical Analysis to Re-Visit Calculus Abstract: A standard undergraduate course in numerical methods assumes that students are very familiar with a number of theoretical ideas from calculus, such as the Intermediate Value Theorem, the Mean Value Theorem, and Taylor's Theorem. All too often, these ideas get short shrift in beginning calculus, as students generally tend to focus most of their effort on learning techniques of symbol manipulation. This talk will give an overview of a new approach to teaching numerical analysis that utilizes a constructive approach to mathematics, which allows the student to take a new look at these calculus ideas in the context of algorithm construction. The talk will also include a constructive proof of the Mean Value Theorem. ## Spring 2009 April 15 Dr. Sungkon Chang and William Nathan Hack Maximizing the Minimum Mutual Distance (Preliminary Report) Abstract: In this talk we shall introduce the problem of maximizing the minimum mutual distance. This problem is in fact in the heart of coding theory, but its obvious analogue to Euclidean space is also very interesting. We began to investigate some cases, and the main part of the talk will be a preliminary report on our investigation. April 1 The Armstrong Putnam Team Reflections on the 69th Annual Putnam Mathematical Competition Abstract: On December 6, 2008, an intrepid team of Armstrong students spent most of their Saturday working on a dozen frighteningly challenging mathematical problems. Why? Just another installment of the notoriously difficult William Lowell Putnam Mathematical Competition. Members of the team will discuss solutions of their favorite problems from the most recent competition. March 11 Dr. Jared Schlieper, Mathematics An Introduction to Convex Bodies Abstract: If we slice the cube through its center, in which direction will the slice have greatest area? We will begin by answering the classic problem of slicing a cube in R3 and then move on to Rn. We then see how the problem led to the recent use of the Fourier transform in solving some classic problems with volumes of convex bodies. Finally, we will examine some recent research efforts related to the cube slicing problem. February 19 Jeanette Olli, University of North Carolina at Chapel Hill An Introduction to Dynamical Systems Abstract: There are many things that are unpredictable that people try to predict, such as the weather. Dynamical systems involve studying a system's long term behavior. After providing a definition of what a dynamical system is, we will look at several examples of dynamical systems and properties of them that we can study. One type of dynamical system is a substitution system, which is defined by a particular substitution in either one or two dimensions. A 2-dimensional example of this is a tiling system, which is a covering of the plane by particular tiles that fit together with no overlap. We'll also look at several examples of those and some of their properties. February 4 Nova Films Hunting the Hidden Dimension: A NOVA film about fractals. Abstract: You may not know it, but fractals, like the air you breathe, are all around you. Their irregular, repeating shapes are found in cloud formations and tree limbs, in stalks of broccoli and craggy mountain ranges, even in the rhythm of the human heart. In this film, NOVA takes viewers on a fascinating quest with a group of maverick mathematicians determined to decipher the rules that govern fractal geometry. ## Fall 2008 November 12 Dr. Sungkon Chang The Birch and Swinnerton Dyer Conjecture and Quadratic Twists of an Elliptic Curve. Abstract: Solving an equation is a fundamental problem in mathematics, and in number theory, solving a polynomial equation of two variables for rational solutions is a well-known difficulty problem. In this presentation Dr. Chang will introduce the basic theory of cubic equations of two variables known as elliptic curves, and present his research results in this area. The immensity of the arithmetic of elliptic curves was revealed to the mathematics community when the proof of Fermat's Last Theorem was completed in 1995 by Sir Andrew Wiles et al proving a conjecture about elliptic curves, called the Taniyama-Shimura-Weil Conjecture. One of the most prominent problems to solve in the theory of elliptic curves today is the Birch-and-Swinnerton-Dyer Conjecture. This conjecture asserts that some analytic complex-valued generating function L(s), called an L-function, associated with an elliptic curve reveals a pack of arithmetic information about the elliptic curve in its Taylor expansion at s=1. Many number theorists in this area are interested in proving a probabilistic implication of this conjecture on a certain family of elliptic curves, called the quadratic twists of elliptic curves, and Dr. Chang will introduce the literature and his work in this area. October 29 Dr. Paul Hadavas Operations Research: The Time of Your Life Abstract: Operations Research(OR) has officially been a field of study in mathematics for almost 60 years. But what is it and how does it affect your daily life? In this talk, we'll dig a little deeper into Operations Research, recently dubbed "the science of better", and look at four examples from every day life where OR techniques can be applied. These examples include: • brewing beer • electing a president • getting home the quickest • spending$700 billion in the most efficient way

In addition, we'll examine how different mathematical formulations for these problems can lead to optimal solutions within seconds instead of hours.

October 8
Dr. Selwyn Hollis

Turing Instability and the Leopard's Spots
Abstract: In a 1952 paper, The Chemical Basis of Morphogenesis, Alan Turing explained that spatial patterns of chemical concentration can be generated by simultaneous reaction and diffusion processes, suggesting that this behavior may account for the development of some animal pigmentation patterns such as a leopard's spots. In this talk, Dr Hollis will present an introduction to reaction-diffusion equations and outline the mathematical basis for Turing's theory of pattern formation, which has become known as Turing (or diffusion-driven) instability. Several Mathematica-generated animations will provide illustration.

September 17
Dr. Jim Brawner

Playing with Polyhedra
Abstract: What do Plato, Archimedes, Johannes Kepler, and Norman Johnson have in common? They each have a class of polyhedra named after them. We will survey a variety of polyhedra, some better known than others, and explore some interesting properties and relationships among them.

Spring 2006

April 5

Elijah Allen
Prime Constellations
Consider a k-tuple of prime numbers in ascending order. Such a k-tuple is considered inadmissible if there are no other k-tuples of prime numbers that match its intervals between successive primes exactly. Thus, admissible k-tuples of primes establish a pattern that is repeatable with other k-tuples of primes. An admissible k-tuple with the smallest possible difference between the last and the first terms is defined to be a prime constellation with k terms. The prime k -tuple conjecture states that every admissible pattern for a prime constellation occurs infinitely often. This research looks into this still-open question and gives results so far.

March 22
Dr. Robert L. Taylor, Clemson University

Fun and Opportunities in Probability and Statistics
Probability and statistics problems have intrigued and puzzled people for many years. Dr. Taylor will analyze some of these problems to determine logical solutions and to illustrate facetious approaches to solutions. He will present Monty Hall's "Let's Make a Deal" puzzler as one example of illogical and logical solutions. In addition, Dr. Taylor will discuss career opportunities for students in the mathematical sciences, especially probability and statistics.

March 8
Dr. Jim Brawner, Jeremiah Eisenmenger, Duc Huynh

Reflections on the 2005 Putnam Exam
The Armstrong student team for the 2005 Putman Exam in Mathematics will present a synopsis of their experiences in taking this challenging national examination. Each of the three team members will discuss a solution for one of the problems on the examination.

March 1
Dr. Ray R. Hashemi

A Signature-Based Predictive System for Liver Cancer
Dr. Hashemi will present a hybrid predictive system that improves the prediction of liver cancer caused by a group of chemical agents. The system employs both SOM net and Hopfield net. The SOM net performs the clustering of the training set and delivers a signature for each cluster. Hopfield net treats each signature as an exemplar made up of 2,717 × 2,717 digits and then learns the exemplars. Each record of the test set is also converted into a vector of 2,717 elements and is considered a corrupted signature. The Hopfield net tries to un-corrupt the test record through several iterations using its associative memory property and then attempts to map it to one of the signatures and consequently to the prediction value associated with the mapped signature.

February 22
Amy Chambers, University of Colorado at Boulder

Cuntz Algebras
If E is a directed graph, the graph C*-algebra C*(E) is the universal C*-algebra generated by families of partial isometries and projections corresponding to the edges and vertices of the graph E satisfying certain relations that form a Cuntz-Krieger E-system. Graph C*-algebras have been much studied in the last ten years by D. Pask, A. Kumjian, and I. Raeburn and have proved useful in the general structure theory of C*-algebras. In this talk we will examine the question of the existence of a conditional expectation from the tensor product of two graph C*-algebras, C*(E1) ⊗ C*(E2 ), to the subalgebra B = span{SmSv* ⊗ Sa Sb* : m and v are paths in E1 with the same source, a and b are paths in E2 with the same source, and |m| - |v| = |a| - |b|}. Using an action of the unit circle T on C*(E1) ⊗ C*(E 2), we will show that there always exists a conditional expectation from C*(E1) ⊗ C*(E2) onto B. We will then define a directed graph e derived from the graphs E1 and E2 and examine two examples. In our first example, the conditional expectation maps O d1 ⊗ Od2 , the tensor product of two Cuntz algebras, onto B = C*(e) = Od1d2. The second example we give exhibits a case in which C*(E) does not equal B. Finally, with these two examples in mind, we will make precise the requirements necessary for C*(E) to be equal to our subalgebra B.

February 15
Dr. Charles W. Champ, Georgia Southern University

Using Multiple Characteristics In Quality Assessments -Properties of Multivariate Control Charts with Estimated Parameters.
In this presentation, Dr. Champ will discuss his and co-author L. Allison Jones-Farmer’s research into Hotelling's T², multivariate exponentially weighted moving average (MEWMA), and several multivariate cumulative sum (MCUSUM) charts. Traditionally, these types of charts track varying attributes of a product or service over time. He will present two descriptions of each chart, with estimated parameters for monitoring the mean of a vector of quality measurements. For each chart, one description explains how the chart can be applied with estimated parameters in practice and the other description is useful for analyzing the run length performance of the chart. Run lengths are important in quality control because they offer information about the expected time until a “false alarm” (i.e., a stop-the-manufacturing-line signal that is erroneous). Dr. Champ demonstrates that, if the covariance matrix is “in control”, the run length distribution of most of these charts depends only on the distributional parameters through the size of the process shift in terms of statistical distance. Simulation is used to provide performance analyses and comparisons of these charts. Dr. Champ presents an example to illustrate the MCUSUM and MEWMA charts when parameters are estimated.

February 8
Jim Brawner

The Marriage Problem
As Valentine’s Day approaches, you may be wondering about a strategy for finding the spouse of your dreams. (Then again, you may consider advice on dating from a mathematician to be about as helpful as an ethics seminar conducted by Jack Abramoff. ) In this talk, Dr. Brawner will discuss the problem of finding an optimal strategy for pairing men and women into stable marriages based on their preferences for the members of the opposite sex. In addition to offering at least one genuine piece of advice for marriage seekers, Dr. Brawner will discuss why this problem might be of particular interest to pre-med, pre-law, and economics majors.

February 1
Tim Ellis

The Complete Dummy's Guide to the Greatest Unsolved Problem in Mathematics
In 1859, Bernhard Riemann was appointed a corresponding member of the Berlin Academy, based on his 1851 doctoral dissertation and his 1857 work on abelian functions. In response to this honor, he submitted a paper entitled "On the Number of Prime Numbers Less Than a Given Quantity". In this paper, he presented an educated guess (since known as the Riemann Hypothesis), which is arguably the greatest unsolved problem in all of mathematics. The purpose of this presentation is to explore the background of the Riemann Hypothesis, to shed some light on its meaning, to delve into the history of attempts to prove or disprove it, and to describe the current prognosis of a solution. This presentation will be fully understandable by anyone possessing a passing familiarity with complex numbers and Calculus I.

January 18
Selwyn Hollis

Nuts and Bolts of Nonlinear Optimization
In the latter half of the 20th century, advances in computing technology spurred numerous scientific and mathematical fields. Among them is the field of optimization, which in its broadest sense overlaps significantly with operations research, numerical analysis, the calculus of variations, and optimal control theory. However, the field known to today's applied mathematics community as optimization is essentially a subfield of numerical analysis that deals with algorithms for optimization (minimization or maximization) of functions, with emphasis on efficiency and applicability to large-scale problems, i.e., problems involving a large number of variables. While linear programming is a fairly common topic in a variety of settings, nonlinear optimization/programming is a relatively small discipline that seems oddly obscure within the broader mathematics community, even though multivariable calculus, linear algebra, and basic real analysis provide sufficient background for its study. In this talk, Dr. Hollis describes some of the fundamental problems and algorithms in nonlinear optimization and gives a brief outline of its history.

CST Colloquium