Weekly Calendar

October 22-26, 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, OCTOBER 22

  
RAP ``Etale cohomology'',  159 Altgeld Hall,  10:00 a.m.
  
Bin Wang (Graduate Student, UIUC)
Comparison of topologies

  
Math 400 - Introduction to Graduate Mathematics,  245 Altgeld Hall,  4:00 p.m.
  
Susan Tolman (Associate Professor, UIUC)
Symplectic geometry and group actions

  
Special Applied Math Seminar,  241 Altgeld Hall,  4:00 p.m.
No meeting this week

  
VIGER: Math 500,  243 Altgeld Hall,  4:00 p.m.
  
Chris Willett (Graduate Student, UIUC)
A neophyte's view of contact structures in mathematics


TUESDAY, OCTOBER 23

  
Symplectic and Contact Geometry RAP,  143 Henry Bldg,  10:00 a.m.
  
E. Lerman (Associate Professor, UIUC)
SU(2) actions on contact 5-manifolds

  
Max Newman Topology,  345 Altgeld Hall,  11:00 a.m.
  
Dev Sinha (Assistant Professor, Brown University)
Equivariant Bordism Rings

  
RAP ``Spaces of non-positive curvature'',  243 Altgeld Hall,  11:00 a.m.
  
Kim Whittlesey (Visiting Assistant, Professor, UIUC)
The Flat Torus Theorem
  
Abstract: We will show that a proper semi-simple action of a free abelian group of rank n on a CAT(0) space X always corresponds to a translation action of this group on some n-dimensional Euclidean subspace of X. Further algebraic properties of free abelian subgroups of groups acting by isometries on CAT(0) spaces will be analyzed.

  
Probability and Statistics Seminar,  2 Illini Hall,  11:00 a.m.
See listing on Thursday at 1:00 p.m. The University of Illinois-Purdue Colloquium

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
  
Sean Sather-Wagstaff (post doc UIUC)
The associativity formula for Hilbert-Samuel multiplicities

  
Quantum Information Science Seminar,  280 Materials Research Laboratory,  12:00 p.m.
  
John A. Smolin (IBM Research)
Quantum Information, Computation and Remote State Preparation
  
Abstract: Ordinary, or classical information, is part of a larger subject, Quantum Information. Almost all information technology today involves classical information, but quantum information theory has potential in several areas, notably in cryptography, and in vastly speeding up certain otherwise impossibly-hard computations. I will discuss how quantum computers get their enormous power, how people are attempting to build them, and the many obstacles that must be overcome. I will also discuss quantum teleportation and remote state preparation. Quantum teleportation uses two bits of classical communication and one EPR pair to transmit an unknown quantum state, even though the specification of such a state takes an infinite amount of classical communication. We show that, contrary to expectations, transferring a quantum state that is known to the sender requires only one bit of classical communication, if a sufficient number of EPR pairs is available. I will review teleportation and put our new result in context to show why it is surprising.

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
  
Kevin Ford (Assistant Professor, UIUC)
The prime number race
  
Abstract: We will survey many problems, results and conjectures concerning the relative magnitudes of the functions p(x;q,a) for fixed q. Here p(x;q,a) is the number of primes £ x in the progression a modulo q. It is known that for fixed q, all of the functions p(x;q,a) with gcd(a,q) = 1 are asymptotic to x/(f(q)logx), but curious inequities occur. For instance, p(x;4;3) is greater than p(x;4,1) for "most" x. The behavior of such inequities is closely linked to the distribution of non-trivial zeros of Dirichlet L-functions.

  
Differential Geometry Seminar,  347 Altgeld Hall,  1:00 p.m.
No meeting this week

  
Logic Seminar,  241 Altgeld Hall,  1:00 p.m.
  
Slawomir Solecki (Associate Professor, UIUC)
Embedding E1 in the coset equivalence relation (cont.)
  
Abstract: Let G be a Polish group and let H be its analytic subgroup. I will talk about the relationship between the complexity (in the sense of Borel reducibility) of the coset equivalence relation G/H and the existence of a Polish group topology on H preserving the Borel structure of H. In the first talk, I will present the context of the problem and some background material. Later on I plan to present a general theorem on embedding the equivalence relation E1 into G/H including some details of its proof.

  
Geometric Potpourri Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Peter Andrews (Professor, Eastern Illinois University)
Anatomy of a (Possible) Triangle Center
  
Abstract: If X is a point in the plane of triangle ABC, define the AB-parallelian of X to be the segment parallel to AB, with endpoints on the lines determined by the other two sides. There are analogous parallelians through X parallel to the other two sides. The point X is called an ``equi-parallelian'' point if all three parallelians through X have the same length. Is there always such a point in any triangle? If so, is it unique? If unique, is it a ``triangle center?'' If not unique, what is the locus of all equi-parallelian points? In the course of answering these questions, and more that arise along the way, we will see concrete examples of many of the terms and techniques the active and accessible area of mathematics known as ``Triangle Geometry.'' This talk will be suitable for mathematicians of all ages!

In preparation, complete the following homework assignment, taken from a tenth grade geometry text. Solutions will be collected at the start of the talk. Correct solutions from students will be eligible for a valuable prize.

PROBLEM: In the interior a triangle with sides of length 13, 18, and 26 there is a point X with the property that the three ``chords'' of the triangle through X and parallel to the sides of the triangle all have the same length L. Find L.

  
Stochastic and Nonlinear Analysis,  347 Altgeld Hall,  2:00 p.m.
  
Darryl Holm Theoretical Division and Center for Nonlinear Studies, Los Alamos, National Laboratory)
The Navier-Stokes-a model of turbulence
  
Abstract: Large Eddy Simulation (LES) models of incompressible fluid turbulence are typically written as

\breaktialt u + u ·Ñu - nDu + Ñp + f = - divt,          with Ñ·u = 0
where the subgrid-scale stress (SGS) tensor t is quadratic in the fluid velocity gradient Ñu, the pressure is p and the extrenal force is f. In particular, we study LES models whose SGS tensor t takes the form
t = a2 ga * ( Ñu ·Ñu + Ñu·ÑuT - ÑuT·Ñu ),
where ga* is a smoothing operation, e.g., a spatial filter of width a. This model contains the Leray regularization of Navier-Stokes as a special case, when the last term in t is absent. If a® 0 then t vanishes and the LES equations limit to the Navier-Stokes equations. When ga* is inversion of the Helmholz operator, these equations comprise the Navier-Stokes-a model, which is tractable for mathematical analysis.

We will discuss recent results for the analysis and simulation of the LANS-a model, and we will compare its predictions with data from Zagarola's turbulence experiments in the Princeton superpipe.

  
RAP on Geometric Representation Theory,  345 Altgeld Hall,  2:30 p.m.
  
William Haboush, (Professor, UIUC)
Chapter 2 of Chriss and Ginzburg (cont.)

  
Commutative Ring Theory Seminar,  243 Altgeld Hall,  3:00 p.m.
No meeting today

  
Graph Theory and Combinatorics,  241 Altgeld Hall,  3:00 p.m.
  
Tanya Berger-Wolf (Computer Science Department, UIUC)
Bandwidth of Hamming Graphs
  
Abstract: A labeling of a graph is an injective assignment of numbers 1,¼,n to its vertices (an ordering of the vertices). The bandwidth of a labeling is the maximum (over all edges) of the difference of the labels on an edge. The bandwidth minimization problem for a graph is to find a labeling with smallest bandwidth. We discuss the bandwidth minimization problem for Hamming graphs; these are the cartesian products of cliques (the hypercube is a special case). We present a lower bound and a nearly optimal labeling for arbitrary Hamming graphs. This work is joint with Lawrence Harper and Mitch Harris.

  
Study Seminar on Harmonic Analysis,  347 Altgeld Hall,  3:00 p.m.
  
Dr. Jorge Rivera-Noriega (Doob Postdoc, UIUC)
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

  
Mathematics in Science and Society,  245 Altgeld Hall,  4:00 p.m.
  
Darryl D. Holm (Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory)
Pulsons, peakons and solutions of 1+1 evolutionary PDEs that act like billiards
  
Abstract: We discuss novel wave structures present in the class of 1+1 dimensional evolutionary PDEs
mt+umx+b uxm = 0,    u = g*m,   
lim
|x|®¥ 
 u,m = 0 .
Here u = g*m is convolution of m(x,t) with a spatial filter (or Green's function) g(x), and b is a constant. When g is even and bounded, these PDEs yield propagating wave solutions for u(x,t), with shape g. These are the pulsons, and they collide elastically like billiards. For some choices of the function g and the constant b, the solution develops verticality in finite time at inflection points of negative slope. The choice g(x) = e-| x | avoids developing verticality, by avoiding inflection points and introducing a jump in slope at the peak. These are the peakons. For b=2 and b=3, the initial value problem for the peakon equation can be completely solved by using methods from soliton theory.

I will mention how the above PDEs arise in the 1D compressible limit of a new 3D turbulence model called the Navier-Stokes-a model.

  
RAP - Descriptive set theory and Rosenthal compacta,  241 Altgeld Hall,  4:00 p.m.
  
Dominika Polkowska (Graduate Student, UIUC)
The structure of Baire class 1 functions



WEDNESDAY, OCTOBER 24

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
Bin Wang (Graduate Student, UIUC)
Comparison of topologies, (cont.)

  
Math - Physics (BCDE) Lunch Seminar,  336 Mechanical Engr Bldg,  12:10 p.m.
  
John Brodie (SLAC)
The Quantum Hall Fluid
  
Abstract: Using branes in massive Type IIA string theory, and a novel decoupling limit, we provide an explicit correspondence between non-commutative Chern-Simons theory and the fractional quantum Hall fluid. The role of the electrons is played by D-particles, the background magnetic field corresponds to a RR 2-form flux, and the two-dimensional fluid is described by non-commutative D2-branes. The filling fraction is given by the ratio of the number of D2-branes and the number of D8-branes, and therefore by the ratio rank/level of the Chern-Simons gauge theory. Quasiparticles and quasiholes are realized as endpoints of fundamental strings on the D2-branes, and are found to possess fractional D-particle charges and fractional statistics.
Note the unusual day, time, & location.

  
RAP on Quantum Cohomology,  160 English Bldg,  3:00 p.m.
  
Luis Alvarez-Consul (Doob postdoc, UIUC)
``Notes on stable maps and quantum cohomlogy'' by Fulton and Pandharipande
  
Abstract: I will continue with sections 4.2-4.4, which establish several properties of the moduli space of stable pointed maps into projective space (mainly its projectivity).

  
Nonstandard Analysis Seminar,  243 Altgeld Hall,  4:00 p.m.
  
Yevgeniy Gordon (Professor, Eastern Illinois University)
On approximations of locally compact groups by finite quasigroups, III

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Robert Bauer (Assistant Professor, UIUC)
Intersection exponents: Relations between exponents

  
Information Protection Seminar,  114 Coordinated Science Lab,  4:30 p.m.
  
John Jossey (Graduate Student, UIUC)
Counting points on Hyperelliptic and Superelliptic curves using Monsky-Washnitzer Cohomology
  
Abstract: An important problem in Computational algebraic geometry is the enumeraton of points on algebraic varieties over finite fields, or more generally the determination of the characteristic polynomial of the action of Frobenius on a suitable cohomology. Much work so far has been focused on curves of genus one. We will present Kedlaya's algorithm for counting points on an arbitrary Hyperelliptic curve over a finite field Fq of odd characteristic, using Monsky-Washnitzer Cohomology to compute a p-adic approximation to the characteristic polynomial of Frobenius.

THURSDAY, OCTOBER 25

  
Math - Physics (BCDE) Lunch Seminar,  6-110 Engineering Science Bldg,  12:05 p.m.
  
Freddy Cachazo (Harvard)
Geometric Transitions and N=1 Dualities
  
Abstract: A large class of N=1 gauge theories in four dimensions can be geometrically realized in the worldvolume of D-brane probles in Type IIB on local Calabi-Yau threefolds. Geometric transitions taking two-cycles to two-cycles or three-cycles correspond in field theoretic terms to Seiberg-like dualities or to gaugino condensation. Duality cascades are also realized in geometric language as a sequence of transitions ending in gaugino condensation in the deep IR. N=2 A-D-E quiver theories deformed by superpotentials and their affine version are the main example of such field theories. Finally, transitions involving vanishing four-cycles also allow the study of dualities for chiral N=1 quiver theories.

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
  
Sean Sather-Wagstaff (post doc UIUC)
The associativity formula for Hilbert-Samuel multiplicities

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
Favorite proofs
  
Abstract: Proofs in mathematics are often very technical, sometimes tedious, and occasionally downright boring exercises. However, all of us have probably come across some proofs that are the antithesis of this - small gems that are short, non-technical, involve an ingenious idea or have an unexpected twist, proofs that are ``from the Book'', as Erdos would say. Number theory is an area that is particularly rich of such pearls of proofs. In this session, members of the audience are encouraged to present their favorite proofs in number theory in short talks of 10 minutes or less.

  
Group Theory,  347 Altgeld Hall,  1:00 p.m.
  
Nigel Boston (UIUC)
The probability of generating a group
  
Abstract: Building on work of Phillip Hall and Gaschütz, Mann and I independently defined and studied the function P(G,s) that gives the probability of generating a finite (or finitely generated profinite) group with s elements. I will discuss some unusual properties of this function and some applications.

  
University of Illinois-Purdue Colloquium,  Danville, Illinois,  1:00 p.m.
  
Bruce A. Craig (Professor, Department of Statistics, Purdue University)
Assessing the trend of the Florida manatee via aerial surveys: 1982-Present
  
Abstract: In many animal population studies, the construction of a stochastic model provides an effective way to capture underlying biological and sampling characteristics which contribute to the overall variation in the data. In this talk, I will discuss a model used to assess the population trend of the Florida manatee, along the Atlantic coast of that state using aerial survey data collected at winter aggregation sites between 1982 and 2000. This model accounts for the method by which the manatees were counted, their possible movement between surveys, and the potential increase/decrease of the total population over time. We draw posterior inferences on manatee population growth via Markov chain Monte Carlo samples from the Bayesian hierarchical model developed. This study generalizes the well-studied Binomial(N,p) problem where both N and p are unknown. This is joint work with John Reynolds III (Eckerd College) and Richard Levine (UC-Davis).

NOTE LOCATION: Hideaway Bldg., Kennekuk County Park, 22296-A Henning Road, Danville, IL, 61834

  
RAP on Noncommutative Lp spaces,  345 Altgeld Hall,  1:00 p.m. (cont. at 3:00 p.m.)
  
Magdalena Musat (Graduate Student, UIUC)
Noncommutative Martingale BMO and interpolation
  
Abstract: In connection with the noncommutative Martingale-Hardy space H1, G. Pisier and Q. Xu introduced the noncommutative BMO and proved that BMO = (H1)*. We will discuss interpolation results between noncommutative LP-spaces and noncommutative BMO.

  
Algebraic Geometry Seminar,  159 Altgeld Hall,  2:00 p.m.
No meeting this week

  
Algebraic Number Theory,  241 Altgeld Hall,  2:00 p.m.
  
Leon McCulloh (Professor, UIUC)
Relative module structure of rings of integers II
  
Abstract: The first of two lectures on the module structure of rings of integers related to questions about the existence of relative integral or normal integral bases in bases in finite extensions of number fields.

  
Analysis Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Denka Kutzarova (Visiting Associate Professor, UIUC)
On approximate l1 systems in Banach spaces
  
Abstract: We define approximate l1 systems in Banach spaces and give a characterization in terms of spreading models. We also consider the question of existence of quasi-greedy subsequences of the Haar system in L1. (Joint work with S.J. Dilworth and P. Wojtaszczyk)

  
Knot Theory RAP,  345 Altgeld Hall,  2:00 p.m.
  
John Sullivan (Associate Professor, UIUC)
Rational tangles and two-bridge knots
  
Abstract: The bridge number of a knot was related by Milnor to its total curvature. Most (small) alternating knots have bridge number two. This important class can be best understood, following Conway, as numerators of rational tangles. These tangles, generated from the zero tangle by two simple moves, are in one-to-one correspondance with rational numbers, and are related to their continued fractions.

  
Commutative Ring Theory Seminar,  243 Altgeld Hall,  3:00 p.m.
  
Sandra Spiroff (Graduate Student, UIUC)
Limiting Behavior on Restriction of Divisor Classes to Hypersurfaces, (cont.)

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

  
Mathematics Colloquium,  245 Altgeld Hall,  4:00 p.m.
  
Lev Birbrair (Universidade Federal do Ceara, Brazil)
Algebraic Geometry from a Metric Viewpoint
  
Abstract: It is known that algebraic varieties, real algebraic sets and semialgebraic sets have rather nice properties as topological spaces. What properties do they have as metric spaces? We will discuss some recent results stimulated by this question related to Metric and Lipschitz Geometries of algebraic sets.
Refreshments at 3:15 p.m. in Room 321 Altgeld Hall


FRIDAY, OCTOBER 26

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
David Murphy (Graduate Student, UIUC)
Principal homogeneous spaces

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Robert Bauer (Assistant Professor, UIUC)
Intersection exponents: Asymptotic behavior

  
Model Theory Seminar,  141 Altgeld Hall,  4:00 p.m.
  
James Tyne (Graduate Student, UIUC)
titleValuation and Residue Properties for power bounded theories
  
Abstract: Suppose that R is a model of some extension of RCF, and that R < a > is an elementary extension of R, and that these models are equipped with valuations, v,w. The Valuation Property asserts that if the value groups are different, then there is r Î R such that w(a-r) is not in the value froup of R. The Residue Property asserts that if the residue fields are different, then there are c,d Î R such that ca-d witnesses this difference. I will define these terms, state these properties more precisely, and show that these properties hold for power bounded theories.

File translated from TEX by TTH, version 2.01.
On 22 Oct 2001, 14:09.