Weekly Calendar

April 2-6, 2001

Monday Tuesday Wednesday Thursday Friday

Seminars Announcements Conferences Calendar Archive

Items for inclusion in the Weekly Calendar should be submitted via e-mail to Hilda Britt. Deadline for inclusion in the Weekly Calendar is 5 p.m. Thursdays. Speakers are encouraged to provide abstracts.

Orange & Blue Bar

MONDAY, APRIL 2

341 Altgeld Hall, 2:00 p.m.
SPECIAL GEOMETRY SEMINAR
Dr. Andrew M. Kraynik, Sandia National Labs
Diffusion in Random Foams
Abstract: Different pressures in neighboring cells of a dry soap foam cause gas diffusion that leads to coarsening, whereby the average cell radius R grows as the square root of time. In 2D, the growth rate in area of individual cells with n edges is proportional to (n-6). This elegant formula, known as von Neumann's law, is exact. In 3D, the growth rate of individual cells does not depend on number on faces, F, alone, so efforts have focused on finding an average growth law. A mean-field theory, based on Minkowski's theory of mixed volumes, is used to show that the growth rate scales as the square root of F for large F. This is confirmed by simulations in Brakke's Surface Evolver. The role of foam structure and cell topology in 2D and 3D will be compared and contrasted.

Recent developments relating to the structure of random polydisperse foams, and the microrheology of dry soap foams subjected to large quasistatic deformations will also be discussed.

245 Altgeld Hall, 4:00 p.m.
MATH 400 - INTRODUCTION TO GRADUATE MATHEMATICS
Professor Leon McCulloh, Department of Mathematics, UIUC
Fermat, Galois, Kummer, Iwasawa, ... (and me)

TUESDAY, APRIL 3

345 Altgeld Hall, 11:00 a.m.
MAX NEWMAN TOPOLOGY
Jens Hornbostel, Muenster University
A localization theorem in Hermitian K-theory

2 Illini Hall, 11:00 a.m.
PROBABILITY AND STATISTICS SEMINAR
Please see listing on Friday at 4:00 p.m.

243 Altgeld Hall, 12:00 p.m.
SEVERAL COMPLEX VARIABLES SEMINAR
Professor Alex Isaev, UIUC and Canberra
CR structures on spheres

241 Altgeld Hall, 1:00 p.m.
ANALYTIC NUMBER THEORY
Professor Bruce Reznick, Department of Mathematics, UIUC
Patterns of Dependence among Powers of Polynomials
Abstract: Let F = {f1,...,fr} be a family of homogeneous polynomials over \bold C, of degree d in n variables, and let
T(F) = {m \bold N: {f1m,...,frm}    is linearlydependent}.
We are interested in knowing the possible sets which can occur as T(F) for fixed r, n and d. This problem can be completely answered when r £ 3 (Fermat's Last Theorem for polynomials), when d = 1 (Serret's Theorem) and when (r,n,d) = (4,2,2) (related to earlier seminars of mine). A particularly interesting example in this last case is
fk(x,y) = ik x2 + ÷2 x y - i-k y2,       1 £ k £ 4,
for which T(F) = {1,2,5}.

I spoke on this topic last fall in the Commutative Algebra RAP, but have since found many new results. The most substantial result is: THM: |T(F)| £ \frac 12(r-1)(r-2). Also, for prime p, there exists Fp with T(Fp) = {1,2,º,p,p2}.

347 Altgeld Hall, 1:00 p.m.
DIFFERENTIAL GEOMETRY SEMINAR
Dr. Ignasi Mundet i Riera, Madrid
Equivariant bundles and parabolic bundles

243 Altgeld Hall, 1:00 p.m.
LOGIC SEMINAR
Yevgeniy Gordon
Approximation of topological algebraic systems by finite ones
Abstract: We consider approximation of topological universal algebras by finite algebras of the same signature and investigate approximate versions of the first order theorems about topological algebras that hold for approximating finite systems. This is a joint work with W.Henson.

243 Altgeld Hall, 2:00 p.m.
NONSTANDARD ANALYSIS
Professor Yevgeniy Gordon, Visitor, Nizhnii Novgorod State University
Kachurivskii's proof of ergodic theorem based on nonstandard analysis
Abstract: We continue to discuss the Thesis of Kachurivskii, where a new proof of ergodic theorem based on Rokhlin-Halmos Lemma and nonstandard analysis was introduced.

345 Altgeld Hall, 2:00 p.m.
SPACES OF NON-POSITIVE CURVATURE RAP
Misha Gavrilovich and Noah Salvaterra
Berestovsky's theorem and the space of directions

241 Altgeld Hall, 2:00 p.m.
STOCHASTIC AND NONLINEAR ANALYSIS
Professor Steven Williams, Department of Economics, UIUC
Inventing a Theory of Market Mechanisms: An Analysis of the k-Double Auction
Abstract: Different markets are organized in different ways, and the choice of a particular set of rules to govern exchange can influence the efficiency of trading. This talk concerns an effort to develop a comparative theory of market mechanisms. A particular mechanism - the k-double auction - is well-motivated by classical economic theory. A sense in which this mechanism is optimal will be discussed. Depending upon time limits, the talk will mention (i) the use of game theory in modeling the strategic behavior of traders, (ii) some problems in probability theory that arise from modeling incomplete information among traders, and (iii) the numerical solution of differential equations that determine the equilibria.

159 Altgeld Hall, 3:00 p.m.
COMMUTATIVE RING THEORY RAP
Professor Phillip Griffith, Department of Mathematics, UIUC
Projective Schemes, continued

241 Altgeld Hall, 3:00 p.m.
GEOMETRIC POTPOURRI SEMINAR
Professor J. Ralph Alexander, Department of Mathematics, UIUC
Placing a finite pointset inside a rectangle
Abstract: Given a rectangle R and a planar pointset B, does R contain a congruent copy of B? Beginning with ideas of Minkowski, we give one possible method of solution. However, the nature of the problem is greatly affected by one's view on just what a solution should be. We revisit the work of Wetzel, Dunkel, and others for the case of B being a rectangle, and we discuss application of the method when B is a triangle. There is little to report on the corresponding problem for rectangular solids.

345 Altgeld Hall, 3:00 p.m.
GRAPH THEORY AND COMBINATORICS
Professor Jozef Skokan, Department of Mathematics, UIUC
The Regularity Lemma and its applications (Part II: the hypergraph case)
Abstract: In this talk, we point out difficulties in generalization of the Regularity Lemma from graphs to hypergraphs. In particular, we show that the concept of regularity used in the graph case is not sufficient in the hypergraph case.

We present the concept of (d,r)-regularity introduced by Frankl and Rodl, which yields a regularity lemma and a counting argument that allows us to find all small hypergraphs in sufficiently large hypergraphs. If time permits, we also show how this regularity lemma for hypergraphs can be used to deduce results similar to the original Regularity Lemma of Szemeredi.

WEDNESDAY, APRIL 4

College of Law Auditorium, 4:00 p.m.
CENTER FOR ADVANCED STUDY
Larry Smarr, Director, California Institute for Telecommunications and Information Technologies, University of California, San Diego
Back to the Future-The Increasing Importance of the States in Setting the Research Agenda

243 Altgeld Hall, 4:00 p.m.
VERTEX ALGEBRA AND ELLIPTIC GENUS
Iana Anguelova,
Vertex algebras and gerbes, II

114 CSRL, 4:30 p.m.
INFORMATION PROTECTION SEMINAR
Dr. Doug Kuhlman, Motorola Labs
Security in the Business World
Abstract: This will be an informal, non-technical talk about the many aspects of security, as seen from by an academician in a business world. The talk will discuss interoperability (open standards vs. closed standards), intellectual property, protocol design, speed, program size, privacy, balancing conflicting demands, the role of cryptography, and other issues. The general problems surrounding protecting information will be addressed, with no solutions offered.

THURSDAY, APRIL 5

ESB 6.110, 12:00 p.m.
MATH - PHYSICS (BCDE) LUNCH SEMINAR
Dr. Per Berglund, CITUSC Center for Theoretical Physics, University of South California, Los Angeles
Stability of Vector Bundles from F-theory

241 Altgeld Hall, 1:00 p.m.
ANALYTIC NUMBER THEORY
Professor Gwyn Coogan, University of Wisconsin, Madison
Generating functions for certain L-series values
Abstract: In recent papers D. Zagier and Andrews, Ono, and Jimenez-Urroz explored the q-series identities which result when one considers the 'sum of tails' of certain modular forms. In some cases they were able to produce the generating functions for the values of L-series at negative integers. We have found that generating functions of this type are widespread and follow naturally from an analysis, which does not involve the 'sum of tails', of a single variable theta identity, which is similar the the Jacobi Triple Product Identity.

347 Altgeld Hall, 1:00 p.m.
GROUP THEORY SEMINAR
Professor Yevgeniy Gordon
Quantum computations and problems in group theory

241 Altgeld Hall, 2:00 p.m.
ALGEBRAIC GROUPS AND THEIR REPRESENTATIONS
Frobenius Splitting of Sehubert Cells

243 Altgeld Hall, 2:00 p.m.
JOINT ANALYTIC/ALGEBRAIC NUMBER THEORY
Professor Jeremy Lovejoy, University of Wisconsin, Madison
Modular Forms and Arithmetic Properties of Partition Functions
Abstract: There are many natural questions about partition functions which are unattackable using combinatorial techniques or methods from classical analytic number theory. Here we survey some of these questions, explain why the theory of modular forms is relevant, and give a sample of the fascinating results which we now can obtain.

347 Altgeld Hall, 2:00 p.m.
ANALYSIS SEMINAR
Professor Anthony G. O'Farrell, National University of Ireland, Maynooth
Pervasive spaces of analytic functions
Abstract:We describe those open sets U in the sphere such that A(U) is pervasive, and those such that the set of real parts of elements of A(U) is pervasive. A(U) means the uniform algebra of all functions continuous the closure of U and holomorphic on the interior of U. Pervasive means (roughly) that when you remove any nonempty relatively open piece of the boundary of U, then you can approximate all complex-valued (resp. real-valued) functions on the rest of the boundary, uniformly by elements of A(U) (resp. Re A(U)).

141 CSRL, 2:30 p.m.
DECISION, CONTROL, AND OPTIMIZATION SEMINAR
Rene Vidal, Electrical Engineering and Computer Science Department, University of California, Berkeley, Berkeley, California
Multi-Agent Probabilistic Pursuit-Evasion Games with Unmanned Ground and Aerial Vehicles
Abstract: We consider the problem of having a team of Unmanned Ground Vehicles (UGV) and Unmanned Aerial Vehicles (UAV) pursue a second team of evaders while concurrently building a map in an unknown environment. We cast the problem in a probabilistic game theoretic framework and consider two computationally feasible pursuit policies: greedy and global-max. To implement this scenario on real UAVs and UGVs, we propose a distributed hierarchical hybrid system architecture which emphasizes the autonomy of each agent yet allows for coordinated team efforts. We then describe our implementation on a fleet of UGVs and UAVs, detailing components such as high level pursuit policy computation, inter-agent communication, navigation, sensing, and control. We present both simulation and experimental results on real pursuit-evasion games between our fleet of UAVs and UGVs and evaluate the pursuit policies relating expected capture times to the speed and intelligence of the evaders and the sensing capabilities of the pursuers.
NOTE: Coffee and cookies at 2:10 p.m. before the seminar in Room 154 CSRL.

145 Altgeld Hall, 3:00 p.m.
COLORING THEORY RESEARCH GROUP
Discussion of open problems

243 Altgeld Hall, 3:00 p.m.
COMMUTATIVE RING THEORY RAP
Professor Phillip Griffith, Department of Mathematics, UIUC
Projective Schemes, continued

347 Altgeld Hall, 3:00 p.m.
GALOIS MODULES
Marcin Mazur, Department of Mathematics, UIUC
The lifted root number conjecture, continued

245 Altgeld Hall, 4:00 p.m.
MATHEMATICS COLLOQUIUM
Albert Baernstein, Professor of Mathematics, Washington University, St. Louis
The Stretch Conjecture for Lipschitz Functions In Rn
Abstract: In this talk I will discuss a conjectural calculus inequality involving directional derivatives and Jacobian determinants of Lipschitz maps in Rn. The conjecture is suggested by Burkholder's work on sharp inequalities for martingales and has ties to unsolved problems in calculus of variations (rank one functions vs. quasiconvex functions), harmonic analysis (norms of singular operators), quasiconformal analysis (sharp distortion inequalities for quasiregular mappings in Rn) and geometry (it proposes an almost-generalization of the isoperimetric inequality).

Refreshments at 3:15 p.m. in Room 321 Altgeld Hall

FRIDAY, APRIL 6

2 Illini Hall, 11:00 a.m.
PROBABILITY AND STATISTICS SEMINAR
Professor Zhiliang Ying, Department of Statistics, Columbia University
Semiparametric analysis of transformation models
Abstract: I will describe in this talk a new method for estimation of regression parameters in semiparametric regression models, which include the proportional hazards model and the proportional odds model as special cases. It handles the usual right censorship in a natural way. The estimate reduces to that of the maximum partial likelihood in the case of the proportional hazards model. I will also present some limited numerical results.

This is joint work with Kani Chen and Zhezhen Jin.

243 Altgeld Hall, 4:00 p.m.
MODEL THEORY SEMINAR
Professor Anand Pillay, Department of Mathematics, UIUC
Zariski Geometries and Applications

314 Altgeld Hall, 3:00 p.m.
MATHEMATICS IN SCIENCE AND SOCIETY
Professor John Lawrence, University of Waterloo
Group Theory and the Enigma
Abstract: Professor Lawrence will describe his mathematical analysis of the Enigma machine. In the early 1930s a young mathematician, Marian Rejewski, led the Polish cipher bureau's attack on the German military Enigma code machine. His work allowed the Polish cipher bureau to read secret German communications until just before the Second World War. Professor Lawrence will bring a working World War II Enigma machine for demonstration.

This lecture, co-sponsored by CSL and MSS/Department of Mathematics, is part of CSL's Golden Anniversary Spring Lecture Series.

314 Altgeld hall, 4:15 p.m.
MATHEMATICS IN SCIENCE AND SOCIETY
Dr. Simon Singh, author and broadcaster
The Secret History of Public-Key Cryptography
Abstract: Dr. Simon Singh, author of Fermat's Enigma, The Code Book, and The Science of Secrecy, will lecture about the invention of public key cryptography, an incredible encryption system that revolutionized security and allowed the information age to blossom. He will reveal the true story behind its invention, which was until very recently hushed up by the British Government.

Dr. Singh is an author, journalist, and television producer specializing in science and mathematics. Dr. Singh completed a Ph.D. in particle physics at Cambridge University and at CERN in Geneva. In 1990, he joined BBC's Science Department as a producer and director of programs. In 1996, he directed Fermat's Last Theorem, a documentary about the world's most notorious mathematical problem. Most recently he directed a 5-part series called The Science of Secrecy and wrote the companion book. www.simonsingh.com

This lecture, co-sponsored by CSL and MSS/Department of Mathematics, is part of CSL's Golden Anniversary Spring Lecture Series.

There will be a book signing and reception from 5:45-6:45 p.m. at the Author's Corner, Illini Union Bookstore