To confirm times, locations and other details, call the Math/Stat office at 202-885-3120. All talks are in Gray Hall's Bentley Lounge, unless otherwise noted.
April 2008
04/22 /08 3:35pm
Infant Mortality in Pakistan
Mubarka Haq
International labor economist, Bureau of Labor Statistics
Out of a study of 225 countries, the CIA World Factbook ranks Pakistan as the 37th highest country in infant mortality with 70.45 deaths/1,000live births estimated in 2006, where the weighted average falls at 34.44 deaths/1,000live births and the median at 20.32 deaths/1,000live births. While there are several socioeconomic factors accounting for these statistics which require long term strategic planning, it is imperative, in the interim, that a short term solution be developed to help reduce infant mortality in Pakistan. For the purpose of this paper we concentrate on one province of Pakistan – the Province of Punjab. We analyze various health and non-health variables in the 34 districts of Punjab to uncover which variables are most influential and how these variables affect the incidence of infant mortality in this province. We evaluate the availability of prenatal care programs within the areas for expectant mothers and compare infant mortality among those who participated in the program with those who did not. Finally to the extent possible we compare Punjab infant mortality rates to other areas of Pakistan and analyze government policy in this area as it has affected the establishment of preventive programs.
04/08 /08 3:35pm
The Analysis of Bivariate Truncated Data Using the Clayton Copula Model
Antai Wang, Ph.D.Department of Biostatistics, Bioinformatics and Biomathematics, Georgetown University
In individuals infected with human immunodeficiency virus (HIV), distributions of quantitative HIV RNA measurements may be highly left-censored due to values falling below assay detection limits (DL). It is of the interest to find the relationship between plasma and semen viral loads. To address this type of problem, we developed an empirical goodness-of-fit test to check the Clayton model assumption for bivariate truncated data. We also used truncated tau to estimate the dependence parameter in the Clayton model for this type of data. It turns out that the proposed methodology works for both truncated and fixed left censored bivariate data. The proposed test procedure is demonstrated using an HIV data set, and statistical inference is drawn based on corresponding test result. A possible extension of the proposed method is also discussed for other Archimedian copula models.
04/04 /08 7:30pmWard Hall, Room 1
Math in the Movies
Tony DeRose of Pixar Animation Studios will provide a behind the scenes look at the role of mathematics in this revolution.
Filmmaking is undergoing a digital revolution brought on by advances in computer technology, computational physics, geometry, and approximation theory.
Fool’s Feast dessert party to follow in Gray Hall
04/01 /08 3:35pm
A Surface of Constant Negative Curvature and a Related Meromorphic Function
Richard Holzsager, Ph.D.
Professor EmeritusDepartment of Mathematics and Statistics, American University
Investigation of a nicely symmetric surface in three-space led to an interesting complex function. Come see pretty pictures, visual and numerical patterns, and some unanswered questions.
March 2008
03/25 /08 3:35pm
Energy Minimization Techniques to Find The Right Shapes in Images
Gunay Dogan, Ph.D.
Department of Computer and Information Science, University of Pennsylvania
Through the last two decades, the field of image processing has seen significant increase in the use of energy minimization methods. These methods are usually based on partial differential equation formulations and involve iterative update of a candidate solution with respect to an assigned energy, to achieve a "best" solution. An important class of such problems falls under the task of image segmentation, that is, finding distinct objects or regions in given images.Applications range from detection of people in surveillance images to 3d visualization of human organs from medical scans. In this talk, we approach these problems from a shape optimization point of view and introduce a novel iterative method to find the minimum energy shapes in given images. In our method, we model the geometry explicitly, respecting the continuous structure of the problem, and discretize the resulting formulation using the finite element method. A distinct feature of our method is that it allows to apply specially-designed gradient descent schemes tuned for specific applications. We demonstrate the power of this new method with several examples in 2d and 3d.
03/04 /08 3:35pm
Developments of Harmonic Maps and Wave Maps
Prof. Yuan-Jen ChiangDepartment of Mathematics, University of Mary Washington
Harmonic maps between Riemannian manifolds are the critical points of energy functionals. In terms of Euler-Lagrange equations, they satisfy second order non-linear partial differential equations. They were introduced and established by James Eells and Joseph H. Sampson in 1964. We will discuss the history and developments of harmonic maps. Biharmonic maps were first studied by Guoying Jiang in 1986, which generalize harmonic maps. We will discuss a few results of my research in harmonic maps and biharmonic maps. Wave maps are harmonic maps on Minkowski spaces. In this decade there are many new developments in wave maps. We will introduce my two recent joint papers in exponential wave maps and transversal wave maps.
February 2008
02/26/08 3:35pm
Clickers and ConcepTests
Sacha ForgostonDepartment of Mathematics, American University
If you are curious about the use of clicker technology in the classroom, then this talk is for you! I will explain how the technology works, what it can do, and why it is worth using. Additionally, I will present my experience using clickers in Finite Math (Math 150 and 151) courses. Clickers are used by students to answer various types of questions. My preference is to ask conceptual questions called ConcepTests. After the ConcepTest is posed to the class, students vote for an answer. After this, several minutes are allowed for the students to discuss the question and its answer, whereupon they vote once again. This use of ConcepTests is part of a pedagogical method called Peer Instruction which was developed by Eric Mazur in the 1990s for use in his physics classes. Peer Instruction is enjoyable for most students, and it has proven to be effective in increasing student retention. The development and the current state of ConcepTests in mathematics will be discussed. Several examples of ConcepTests that can be used for calculus courses also will be included.
January 2008
01/29/08 3:35pm
Groups and duality,from Pontryagin to Tannaka to Drinfeld
Thomas J. Haines, Ph.D.Department of Mathematics, University of Maryland
Given a group, one may consider its representations, and often information about those representations yields rich information about the group itself. In a certain sense, it is even the case that "the representations determine the group". This kind of duality statement has many avatars. I will explain the earliest ones, due to Pontryagin and then Tannaka. I will also explain a related theme, whereby one recovers certain geometric objects attached to a group (e.g. its flag variety, spherical building, etc.) from the representations of the group. The basic idea behind this last theme is due to Drinfeld, and it plays a role in recent developments in the Langlands program.
November 2007
11/27/07 3:35pm
Gaussian and Stable Random Fields: Their Analytic and Geometric Properties
Yimin Xiao, Michigan State University & SAMSI
Various classes of Gaussian and stable random fields arise in probability theory, statistics and in a wide range of applications. Examples include fractional Brownian motion, the Brownian sheet, solutions to stochastic heat and wave equations, and linear and harmonizable fractional stable motions.In this talk we first give a survey on different classes of random fields, focusing on their self-similarity, long range dependence and heavy-tails. Then we present some recent results on analytic and geometric properties of these random fields.
11/06/07 3:35pm
Model Theory
Alexei S Kolesnikov, Mathematician/Logician, Towson University
Model theory is a subfield of mathematical logic that studies classes of mathematical structures and has interesting connections to algebra, functional analysis, and number theory. I will survey some of the model-theoretic concepts and methods, and will describe some of the goals and achievements of the field. To illustrate the basic concepts, I will sketch a proof of the theorem stating that every one-to-one polynomial map from a Cartesian power of the field of complex numbers into itself is necessarily a bijection.
October 2007
10/26/07 7:30pm
Mathematics and the Art of M.C. Escher
Doris Schattschneider, Professor, Moravian College
The imagery in M.C. Escher's graphic works not only makes obvious use of geometry, but often provides visual metaphors for abstract mathematical concepts. This slide lecture will examine mathematical concepts implicit in several of Escher's works, outline the transformation geometry that governs his interlocking figures, and reveal how this "math anxious" artist actually did pioneering mathematical research in order to accomplish his artistic goals. Escher's mathematical curiosity and insight has been the inspiration for many mathematicians, scientists, and artists of today who seek solutions to problems (both mathematical and artistic) first posed by Escher himself.
Location
: Kogod School of Business, room 118. Desserts will be served in Bentley Lounge afterwards. Main Campus Map
10/23/07 3:35pm
Researching Mathematics and Statistics: What AU Library has to Offer
Anne Osterman, Librarian, American University
Feel overwhelmed when you have to find data? Want a quick place to send your students when they need to find materials for a project? This presentation will give an overview of what AU Library has to offer, including licensed resources and finding aids for materials located on the world wide web. Special emphasis will be given to the Library's newer additions, including Historical Statistics of the United States, the United Nations Common Database, the Encyclopedia of Mathematics and Statistics, and Global Development Finance Online.
0/09/07 3:35pm
AU's Rare Math Book Collection
Susan McElrath, Team Leader for University Archives and Special Collections American University Library
Susan McElrath is the Team Leader, Special Collections and University Archivist. She will introduce and present a collection of historical mathematics books. These valuable and rare books are part of the special collection in American University.
Location
: Archive Reading Room, Room 320, American University Library
September 2007
09/25/073:35pm
A Bayesian IRT Model for the Comparison of Survey Item Characteristics under Dual Modes of Administration
Lou Mariano, Ph.D.
Statistician, RAND Corporation
Ordinal scale survey response items are often used in quantifying a latent trait. When the survey is offered in multiple modes of administration, e.g., telephone interview or self-administered questionnaire, the mode of administration may affect the characteristics of the survey items, such that an individuals responses may differ depending on the mode. Using a mental health survey as a case study, the Bayesian Differential Mode Effects Model (BDMEM) is introduced as an Item Response Theory (IRT) model-based solution for the detection, quantification and reconciliation of mode of administration effects at the item, response category, and scale levels. The BDMEM is compared to the popular approach of differential item functioning (DIF), and its advantages over DIF are highlighted, including the optimal use of repeated measures, the detection of differences in categorical response probabilities, and the automatic equating of results under different modes.
April 2007
04/17/073:30 PM
Enumerative Geometry of Algebraic CurvesArtur Elezi Given 4 lines in a compact, three dimensional space, how many lines meet them? Questions of this type are the focus of enumerative geometry of algebraic curves. We will briefly tour the history of this subject and explain how recent ideas from physics are providing a new framework for formulating and answering some classic problems/conjectures in the field.
March 2007
03/30/077:30 PM
Beaucoup Sudoku: The Sudoku MystiqueDr. Laura Taalman
Dr. Laura Taalman is one of the leading authorities on the mathematics of sudoku. Join us as she reveals themysteries of all things sudoku. Find out how sudoku puzzles and their variants are linked to other mathematical topics, including magic squares, polyominos, knight tours, graph colorings, and many others. Catch a glimpse ofexciting new sudoku variants, such as snowflakes, pyramids, jigsaws, and worms. Try your hand at solving some of the puzzle handouts she will provide. This will be a fascinating evening, as Dr. Taalman exposes allsides of sudoku, from the serious to the whimsical.
March 2007
03/14/073:35 PM
DependenceWei Biao Wu, Statistics, University of Chicago
Dependence plays a fundamental role in statistics. In the talk I will introduce a different concept of dependence. The viewpoint provides new insights in the study of complicated random systems. I will also discuss relations with nonlinear system theory, experimental design, information theory, risk-metrics theory and high dimensional covariance matrices estimation.
February 2007
02/27/073:30 PM
A Novel Asymmetric Distribution with Power TailsPresenter: J. Rene van Dorp, Engineering Management and Systems Engineering Department, George Washington University.Joint work with: Amita Singh and Thomas A. Mazzuchi.
In this talk, we propose a four-parameter asymmetric doubly-Pareto uniform (DPU) distribution with support on the real linem whose density and cumulative distribution functions are constructed by seamlessly concatenating the left and right Pareto tails with a uniform central part. Properties of the distribution are described and a maximum likelihood estimation (MLE) procedure for its parameters is obtained. Two illustrative examples of the MLE procedure are provided. The first example utilizes an i.i.d. sample of standardized log-differences of bi-monthly 30-year U.S. conventional mortgage interest rates (1971-2004). The second example deals with the height of 100 female Australian athletes.
