Weekly Calendar

September 24-28, 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, SEPTEMBER 24

  
RAP ``Etale cohomology'',  159 Altgeld Hall,  10:00 a.m.
  
Mr. Joshua Mullet
Direct and inverse images of sheaves

  
Math 400 - Introduction to Graduate Mathematics,  245 Altgeld Hall,  4:00 p.m.
  
Professor Bruce Berndt
Number Theory: The Queen of Mathematics


TUESDAY, SEPTEMBER 25

  
Symplectic and Contact Geometry RAP,  143 Henry Bldg,  10:00 a.m.
  
Chris Willett
Contact circle actions on three manifolds
  
Abstract: The work of R. Lutz concerning the existence and classification of invariant contact structures on three dimensional principal circle bundles will be discussed. The work of Y. Kamishima and T. Tsuboi on the general classication of circle invariant contact structures on three manifolds will be discussed as well.

  
Max Newman Topology,  345 Altgeld Hall,  11:00 a.m.
  
Chris French (UIUC)
Title is: TBA II

  
RAP ``Spaces of non-positive curvature'',  243 Altgeld Hall,  11:00 a.m.
  
Craig Davis (UIUC)
CAT(0) cubical complexes (cont.)
  
Abstract: We will describe so called ``cubical complexes" which are spaces obtained by gluing a collection of euclidean cubes along isometries between their faces. An explicit combinatorial condition will be given which ensures that such a complex is a CAT(0)-space.

  
Probability and Statistics Seminar,  2 Illini Hall,  11:00 a.m.
  
Professor Jason P. Fine (Department of Statistics and Department of Biostatistics & Medical Informatics University of Wisconsin, Madison)
Comparing Non-Nested Cox Models
  
Abstract: The limiting distribution of the partial likelihood ratio is studied under the most general conditions. The multiplicative hazards models being fitted may be non-nested and misspecified. The true model is not assumed to contain either of the models under consideration. The null hypothesis is that the fitted models are equidistant in Kullback-Leibler metric applied to the rank likelihood. The estimated information criterion is consistent for the model which is closer to the truth. However, its distribution may depend on the unknown data generating mechanism. A sequential testing procedure is proposed for non-nested comparisons which is valid regardless of the true model. This involves a novel statistic for the equality of the fitted models which is separate from the partial likelihood. The methodology has important applications in model assessment. A real example illustrates its utility in selecting the functional forms of covariates and relative risks.

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
  
Professor Robert Kaufman
Function Algebras and Several Complex Variables, IV

  
Quantum Information Science Seminar,  280 Materials Research Laboratory,  12:00 p.m.
  
Dr. David Branning (Department of Physics, UIUC)
The Quantum Eraser

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
  
Dr. Johnson F. Yan
The Prime Number Code: A method of protein structure prediction derived from the genetic code
  
Abstract: A mathematical method has been developed in which the genetic code is interpreted numerically. Amino acids are ``translated" into natural numbers, and the properties of polypeptides are then predicted according to number theory principles. Distributions of prime quartets are analogous to recurring frequencies of amino acids, tripeptides and heptapeptides. Secondary structural elements-helices and beta-strands-are detected from consecutive and overlapping prime heptapeptides and tripeptides. Beta-strand tripeptides and helical heptapeptides have axial lengths of one nanometer. A mixed strand protein tends to form a cubic bundle. This new bioinformatics approach has been used to predict structural motifs in proteins whose structures have already been determined.

  
Differential Geometry Seminar,  347 Altgeld Hall,  1:00 p.m.
  
Susan Tolman
Kirwan surjectivity for loop group actions
  
Abstract: Let a compact Lie group G acts on a symplectic manifold M with a proper moment map F. Kirwan showed that the restriction map from the equivariant cohomology of M to the ordinary cohomology of the reduced space is a surjection. We show that the same result is true for loop group actions. We discuss the relationship with group valued moment maps and the cohomology of the moduli space of flat connections. Based on joint work with J. Weitsman

  
Logic Seminar,  241 Altgeld Hall,  1:00 p.m.
  
Wai Yan Pong
On ranks of definable groups in certain w-stable theories
  
Abstract: We give a criteria on certain w-stable theories which guarantee Morley rank and U-rank agree for definable groups. This is a mild generalization of a similar result obtained by Pillay and Pong on differentially closed fields.

  
Geometric Potpourri Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Professor Jeff Erickson (UIUC Department of Computer Science)
Arbitrarily large neighborly families of congruent symmetric convex 3-polytopes
  
Abstract: I will describe, for any positive integer n, a family of n congruent convex polyhedra in R3, such that every pair of polyhedra share one common facet. The polyhedra are Voronoi regions of points on the helix (t, cost, sint). This construction answers a forty-year-old open problem of Danzer, Grünbaum, and Klee; the largest such family previously known, discovered by Zaks in 1987, consists of only eight polytopes. A simple modification ensures that each polyhedron in the family is bounded and symmetric. I will also briefly discuss extensions of this construction to higher dimensions. A preprint is available at arXiv:math.CO/0106095, or from my web site at

``http://www.cs.uiuc.edu/ jeffe/pubs/crum.html".

  
Stochastic and Nonlinear Analysis,  347 Altgeld Hall,  2:00 p.m.
  
Rodrigo Banuelos (Purdue University)
Space-time Brownian motion and the Nazarov-Volberg estimate on the Beurling-Ahlfors operator

  
RAP on Geometric Representation Theory,  345 Altgeld Hall,  2:30 p.m.
  
Professor William Haboush
Chapter 2 of Chriss and Ginzburg
  
Abstract: I will continue with chapter three and will review basic Kahler geometry and discuss fixed point reduction and the beginnings of Borel Moore cohomology theory.

  
Commutative Ring Theory RAP,  243 Altgeld Hall,  3:00 p.m.
  
Professor Sean Sather-Wagstaff
Local Chern Characters (cont.)
http://www.math.uiuc.edu/ ssather/MATH/crt_fa01.html

  
Graph Theory and Combinatorics,  241 Altgeld Hall,  3:00 p.m.
  
Professor Alexandr Kostochka
On k-chromatic r-uniform hypergraphs with few edges
  
Abstract: Let m(r,k) denote the minimum number of edges in a (k+1)-chromatic r-uniform hypergraph. Erdös proved that 2r-1 £ m(r,2) £ r2 2r. The best known lower bound now is due to Radhakrishnan and Srinivasan: For every c < 1/Ö2, there exists an r0 = r0(c) such that for every r > r0, m(r,2) ³ c2rÖ{r/lnr}. Erdös and Lovász said once ``perhaps the order of magnitude of m(r,2) is r2r''. Repeating the argument of Erdös, one can see that for every k ³ 2, there exist r = r(k) and C = C(k) such that m(r,k) £ Cr2 kr. The aim of this talk is to outline a proof that there exists an r0 such that for every r > r0,
m(r,4) ³ c4r æ
ç
è 		r
lnr
 ö
÷
ø 		2/3

 
 ,
where c = 0.05.

It seems that by elaborating the proof we can show that for every positive integer l, there exist r0 = r0(l) and c = c(l) such that for every r > r0,

m(r,2l) ³ c(2l)r æ
ç
è 		r
lnr
 ö
÷
ø 		[l/( l+1)]

 
 .

  
Study Seminar on Harmonic Analysis,  347 Altgeld Hall,  3:00 p.m.
  
Dr. Jorge Rivera-Noriega
Harmonic analysis in locally flat domains, cont.
  
Abstract: We are studying the paper of C. Kenig and T. Toro on harmonic analysis in locally flat domains

  
Decision Control Laboratory - Topics in Systems,  141 CSL,  3:30 p.m.
  
Pramod Viswanath (University of Illinois, Coordinated Science Laboratory)
Opportunistic Beamforming: Dumb Antennas and Simple Scheduling
  
Abstract: Traditionally, wireless networks have been built on the principle of making point-to-point links look close to reliable additive white Gaussian noise channels. This design involves spreading and equalization to make the time and frequency varying wireless channel appear flat. In this talk, we make a case that a joint design of physical and network layers of the wireless system can make use of the variation in the wireless channel to gain significant system level benefits. We take a proactive stance and create artificially, larger and faster channel fluctuations when nature does not provide much thus increasing the system level gains. These artificial channel fluctuations are created by using an array of transmit antennas in a ``dumb" way, and the gains are harnessed by a ``simple" scheduler. Finally we distill the lessons learnt into a new design principle for modern data wireless networks.


WEDNESDAY, SEPTEMBER 26

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
Professor Sean Sather-Wagstaff
Cohomology

  
Algebraic Geometry Seminar,  160 English Bldg,  3:00 p.m.
  
Professor Sheldon Katz
Quantum Cohomology
  
Abstract: This talk will be an introduction to quantum cohomology from an algebro-geometric viewpoint. Important results and open problems will be surveyed. Foundational material may be developed in subsequent weeks as a RAP.

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Professor Robert Bauer
3-D Bessel Process

  
Information Protection Seminar,  114 CSRL,  4:30 p.m.
  
Haris Domazet
The cipher RIJNDAEL
  
Abstract: In 1997, the National Institute of Standards and Technology (NIST) initiated a process to select a symmetric-key encryption algorithm to be used to protect sensitive (unclassified) Federal information. >From the fifteen candidate algorithms that were submitted, five finalists were selected and subjected to analysis by the international cryptographic research community. Having reviewed the five finalists, NIST decided to propose RIJNDAEL as the Advanced Encryption Standard. In this talk we describe the cipher RIJNDAEL. Topics include: specification and design rationale, implementation aspects, performance figures, and strength against known attacks.

  
Nonstandard Analysis Seminar,  243 Altgeld Hall,  4:00 p.m.
  
Dr. Petr Andreev (Moscow, currently visiting City College, CUNY)
On axiomatic foundations of nonstandard analysis
(A group will go to dinner with the speaker after his talk.)


THURSDAY, SEPTEMBER 27

  
Math - Physics (BCDE) Lunch Seminar,  6-110 Engineering Science Bldg,  12:05 p.m.
  
Moshe Rozali (University of British Columbia)
D-branes on AdS3

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
  
Bernhard Lamel (Doob Research Asst. Prof)
Mapping Problems in Several Complex Variables, IV

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
  
Professor Heini Halberstam (UIUC)
The Riemann Hypothesis (Survey Talk)
  
Abstract: In 1859 Bernhard Riemann delivered an address ``On the number of primes less than a given magnitude" to the Prussian Academy of Sciences in Berlin. In the course of the lecture he considered a meromorphic function of the complex variable s, zeta(s), now known as Riemann's zeta function, whose non-real zeros all lie in the infinite strip 0 < Re(s) < 1 and, as Riemann showed, have an intimate connection with the distribution of prime numbers. Riemann expressed the opinion that, ``very probably," all these zeros actually lie on the line Re(s)=1/2. This is the Riemann Hypothesis (RH). The aim of this talk is to sketch what is known about RH and to describe such evidence as there is for and against it. It will touch briefly on the nature of current activity related to RH. [The Riemann Hypothesis is one of the seven ``Million Dollar Problems." This talk was first given a year ago as part of a colloquium series on the Million Dollar Problems.]

  
Group Theory,  347 Altgeld Hall,  1:00 p.m.
  
Chris Hruska (Cornell University)
The Relative Hyperbolicity of Groups with Isolated Flats
  
Abstract: Brian Bowditch has explained that Gromov's concept of relative hyperbolicity is actually a very direct generalization of geometrically finite Kleinian groups. A group G is relatively hyperbolic if it admits an action on a Gromov-hyperbolic space X which is ``geometrically finite'' in an appropriate sense. Asli Yaman has recently shown that relatively hyperbolic groups can be completely characterized in terms of properties of their action on the boundary of X. If a group G admits an action on a metrizable compactum M satisfying certain properties, then she shows that G is relatively hyperbolic and that M is the boundary of G.

We use this result to show that a certain class of CAT(0) groups are hyperbolic relative to their maximal abelian subgroups of rank at least two. The groups in question are those which act properly and cocompactly on CAT(0) spaces in which the flat Euclidean subspaces are isolated.

  
RAP on Noncommutative Lp spaces,  345 Altgeld Hall,  1:00 p.m. (cont. at 3:00 p.m.)
  
Professor Marius Junge (UIUC)
Noncommutative martingales inequalities
  
Abstract: Following the work of Xu, Pisier and Randrianantoanina we indicate the order of constants for the noncommutative Burkholder-Gundy, Stein and Doob inequalities.

  
Algebraic Number Theory,  241 Altgeld Hall,  2:00 p.m.
  
Dr. Gebhard Boeckle (ETHZ, Switzerland)
Deformations and the rigidity method
  
Abstract: In the past, the rigidity method proved an important tool in Inverse Galois Theory to construct Galois extensions of the rational numbers, or abelian number fields for a given Galois group. In an example that arises from the p-torsion representation of the coarse moduli space of elliptic curves over the complex numbers, Rohrlich used the rigidity method to realize SL2(Zp[[T]])| as a Galois group over the cyclotomic Zp-extension F of Q(zp+zp-1), such that the specialization T = 0 is related to the representation of the Tate-module of an elliptic curve over F. His methods rely very much on explicit results on universal elliptic curves, moduli spaces, etc. We will sketch a more axiomatic approach by studying deformations of rigid systems. This shows that under rather general hypothesis, one can construct large `p-adic' Galois extensions over cyclotomic Zp-extensions of number fields, or even over abelian number fields. Most of the resulst of Rohrlich can be recovered. The following are two independent applications of our results:

1. There exists a family of totally real surjective Galois representations (unramified outside finitely many places)

rz: Gal( _
Q
 
 /Fz)® SL2(Zp(z+z-1))
where z ranges over all pn-th roots of unity and Fz is an abelian number field depending on z.

2. There exist infinite p-adic analytic Galois extension of functions fields of characteristic different from p which are unramified and contain only a finite constant field. (There are previous examples due to Ihara and Frey-Kani-Völklein.

  
Analysis Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Professor Ilia Binder
Harmonic measure and rotation: multifractal analysis
  
Abstract: We will discuss the fine properties of the harmonic measure and rotation of planar domains. In particular, we will perform the multifractal analysis, and consider the sharp bounds on the multifractal spectra for simply connected and general domains. We will also discuss the relations of the geometry of the boundaries of planar domains with the classical theory of conformal mappings.

  
Knot Theory RAP,  345 Altgeld Hall,  2:00 p.m.
  
Katharine Preedy
Types of Knots

  
RAP on Research Problems in Coloring Theory and Extremal Combinatorics,  241 Altgeld Hall,  3:00 p.m.
Further consideration of research problems

  
Commutative Ring Theory Seminar,  243 Altgeld Hall,  3:00 p.m.
  
Professor Sankar Dutta
On Modules of Finite Projective Dimension over Complete Intersections.
http://www.math.uiuc.edu/ ssather/MATH/crt_fa01.html

  
Combined Faculty and Graduate Student Seminar,  314 Altgeld Hall,  4:00 p.m.
  
Bob Wengert (Department of Philosophy, UIUC)
What are we talking about when we talk about ethics?
  
Abstract: It is Graduate College policy that every academic unit present a combined graduate student and faculty seminar each year which addresses the ethical standards and practices that represent the norms in the discipline. Wengert will provide short case studies and discussion in his presentation ``What are we Talking about when we Talk about Ethics?'' Faculty, postdocs, visitors, graduate students and staff are urged to attend

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


FRIDAY, SEPTEMBER 28

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
Professor Sean Sather-Wagstaff
Cohomology (cont.)

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Robert Bauer
Intersection exponents of planar Brownian motion

  
Model Theory Seminar,  141 Altgeld Hall,  4:00 p.m.
  
Mr. Thomas Rohwer
Module definable sets in a field of Laurent series, III
  
Abstract: Let k be a finite field of characteristic p, K = k((x)) the field of Laurent series over k, and R = K[F] the ring of twisted polynomials over K with respect to the commuting relation Fl = lp F for all l in K. K is a left R module using the natural action of K on K and letting F act as l® lp. Some results on the structure of solution sets of linear equations (and projections of these) in the module K will be presented.

File translated from TEX by TTH, version 2.01.
On 21 Sep 2001, 11:46.