Weekly Calendar

November 26-30, 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, NOVEMBER 26

  
RAP ``Etale cohomology'',  159 Altgeld Hall,  10:00 a.m.
  
Marcin Mazur (Doob Postdoc, UIUC)
Etale cohomology of curves (cont.)

  
Math 400 - Introduction to Graduate Mathematics,  245 Altgeld Hall,  4:00 p.m.
  
Doug West (Professor, UIUC)
Coloring and List-Coloring of Graphs and Hypergraphs

  
Special Applied Math Seminar,  241 Altgeld Hall,  4:00 p.m.
  
Gary Olsen (UIUC Bio.)
Topic: TBA

  
VIGRE: Math 500,  243 Altgeld Hall,  4:00 p.m.
No meeting until December 2001


TUESDAY, NOVEMBER 27

  
Symplectic and Contact Geometry RAP,  143 Henry Bldg,  10:00 a.m.
  
S. Tolman (Associate Professor, UIUC)
Symplectic Geometry and Symplectic Topology
  
Abstract: This is joint work with Dusa McDuff. We will discuss some theorems and conjectures that relate symplectic geometry (that is, Hamiltonian group actions) with symplectic topology, namely the fundamental group of the group of symplectomorphisms.

  
Max Newman Topology,  345 Altgeld Hall,  11:00 a.m.
  
Robert Bruner (Wayne State University)
Deforming representation theory into cohomology theory
  
Abstract: The connective K-theory of a classifying space gives a deformation from the completed representation ring of the group to a ring F-isomorphic to the cohomology of the group. I will discuss what I have learned about these rings in joint work with John Greenlees.

  
Probability and Statistics Seminar,  2 Illini Hall,  11:00 a.m.
  
Professor Arne Bathke (Department of Statistics, University of Kentucky)
Testing the Effect of Covariables in Nonparametric Mixed Models
  
Abstract: Two groups of primary school children are given different instructions on how to start completing a certain pattern, taken from the Wechsler Intelligence Scale for Children (WISC). Do the different instructions result in different average times in completing the pattern, and is this time affected by "field dependence"? We regard "field dependence" as a covariable, and show that a straightforward generalization of Spearman's rank correlation coefficient can be used to analyze this data set.

In fact, Spearman's rho is the special case of a general asymptotic rank-based test on the influence of a concomitant variable in a multi-factorial nonparametric mixed model.

We develop the general test statistic that can be used for data with ties, for ordinal and even for binary data. The finite sample performance of the test procedure is analyzed by computer simulations.

  
RAP ``Spaces of non-positive curvature'',  243 Altgeld Hall,  11:00 a.m.
  
Jeremy Wong (Graduate Student, UIUC)
The boundary at infinity of a CAT(0)-space (cont.)

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
No meeting this week

  
Quantum Information Science Seminar,  280 Materials Research Laboratory,  12:00 p.m.
  
Sergey Frolov (Physics, UIUC)
Designing a superconducting Qubit

  
Abstract: Superconductors look attractive as candidates for quantum computer hardware because of their high integrability, it is now possible to couple thousands of SQUIDs together. However, their potential to carry a quantum state is not yet fully understood. Recently observed coherence of charge (Nakamura et al.) and flux (Friedman et al.) variables gives reasons to beleive that all the reqirements for quantum computer can be met in Josephson circuits. In fact, several different schemes of superconducting qubits were brought forward. I will cover principles of their future operation as well as some physics leading to their creation.

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
  
Ken Stolarsky (Professor, UIUC)
Arithmetic in base B: a selection of digital problems and applications

  
Differential Geometry Seminar,  347 Altgeld Hall,  1:00 p.m.
  
Melissa Liu (Harvard)
Moduli of J-Holomorphic Curves with Lagrangian Boundary Conditions
  
Abstract: Let (X, w) be a symplectic manifold, J be an almost complex structure compatible with w, and L be a Lagrangian submanifold. The stable compactification of moduli of parametrized J-holomorphic curves in X with boundary in L (with prescribed topological data) is compact and Hausdorff in Gromov's C¥ topology. It has a Kuranishi structure with corners in the sense of Fukaya and Ono. This Kuranishi structure is orientable if L is spin. In the special case where the expected dimension of the moduli is zero, and there is an S1 action on the pair (X,L) which preserves J and acts on L freely, we define the Euler number for this S1 equivariant pair and the prescribed topological data. We conjecture that this rational number is the one computed by localization technique using the given S1 action (Katz-Liu, Li-Song, Graber-Zaslow).

  
Logic Seminar,  241 Altgeld Hall,  1:00 p.m.
  
Angsheng Li (Institute of Software of the Chinese, Academy of Sciences, visiting University of Leeds)
Definable Relations On the Computably Enumerable Degrees
  
Abstract: We talk about recent developments in the study of definable relations on the computably enumerable (c.e.) degrees, including structural properties, high/low hierarchy and related hierarchies, elementary differences among jump hierarchies, splitting, nonsplitting and naturally definable relations, continuity in the computably enumerable degrees, in particular, the solution of Lachlan's major subdegree problem, and the Turing approximation of the c.e. degrees in the Ershov hierarchy.

  
Geometric Potpourri Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Herbert Edelsbrunner (Professor, Duke University and Raindrop Geomagic)
Morse complexes and topological persistence
  
Abstract: We consider Morse complexes decomposing a manifold with a smooth height function into regions that have the same gradient flow pattern. We use a combinatorial algorithm with numerical components to construct such a complex via handle slides. A hierarchy of progressively simpler Morse complexes is then constructed by cancelling critical points in pairs. These cancellations are performed in the order of increasing persistence of critical points.

  
Motivic Cohomology Seminar,  159 Altgeld Hall,  2:00 p.m.
  
Sung Myung (Graduate Student, UIUC)
The regulator map for motivic cohomology using the dilogarithm function (cont.)

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

  
Graph Theory and Combinatorics,  241 Altgeld Hall,  3:00 p.m.
  
A. Kostochka (Professor, UIUC)
Graphs with small Ramsey numbers
  
Abstract: For a graph G, the Ramsey number R(G,G) is the minimum positive integer N such that in every 2-coloring of edges of the complete graph KN there is a monochromatic copy of G. A family F of graphs is linear Ramsey if there is a constant C such that R(G,G) £ C |V(G)| for every G Î F. Burr and Erdos conjectured that for every d, the family Dd of d-degenerate graphs is linear Ramsey, where a graph is d-degenerate if each subgraph has a vertex of degree at most d. Kostochka and Rödl proved recently that at least Dd is `polynomial Ramsey'. For n > d, we say that a graph H is (d,n)-common if every set of d vertices in H has at least n-d common neighbors in H. Every (d,n)-common graph contains every d-degenerate graph on n vertices. In view of this, Frieze and Reed asked whether for every positive integer d, there is a constant C such that for every graph H on Cn vertices, either H or its complement contains a (d,n)-common subgraph.

A positive answer would imply the Burr-Erdos Conjecture. In this talk we show that the answer to the original question of Frieze and Reed question is `No', but we prove a `Yes' answer for the following polynomial approximation to it. For every e > 0 and positive integer d, there a constant C such that for every positive integer n and every graph H with Cn1+e vertices, either H or it complement contains a (d,n)-common subgraph.

(This is joint work with B. Sudakov.)

  
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

  
RAP - Descriptive set theory and Rosenthal compacta,  241 Altgeld Hall,  4:00 p.m.
  
Slawomire Solecki (Associate Professor, UIUC)
Rosenthal compacta: definitions and examples


WEDNESDAY, NOVEMBER 28

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
Marco Schlichting (Doob Postdoc, UIUC)
Proper base change theorem

  
RAP on Quantum Cohomology,  160 English Bldg,  3:00 p.m.
  
Xinyun Zhu (Graduate Student, UIUC)
Continuing Chapter 5 and beginning Chapter 6

  
Nonstandard Analysis Seminar,  243 Altgeld Hall,  4:00 p.m.
  
Peter Loeb (Professor, UIUC)
The Best way to differentiate measures and the connection with a fundamental operator in analysis
  
Abstract: The first talk uses no nonstandard analysis. It deals with measure differentiation, and is background for what comes later. We show that there is an optimal way to differentiate measures when given a consistent choice of where zero limits must occur. The appropriate differentiation basis is formed following a pattern similar to an optimal approach system for producing boundary limits in potential theory. Applications include the existence of Lebesgue points, approximate continuity, and liftings for the space of bounded measurable functions.
This is joint work with J. Bliedtner.

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Robert Bauer (Assistant Professor, UIUC)
Values of Brownian intersection exponents I

  
Special seminar,  241 Altgeld Hall,  4:00 p.m.
  
Robert Ghrist (Georgia Tech)
Braid Shortening
  
Abstract: Most dynamical systems possessing a parabolic nature exhibit a monotonicity in the dynamics which entwines some underlying local geometric features. A simple example is the "comparison principle" for scalar uniform parabolic PDE's, interpreted as separating tangencies of curves. Borrowing some ideas from knot theory, I will describe a globalization of this principle which lifts the dynamics to spaces of braids and uses Morse-theoretic techniques to force stationary solutions. Applications of this general forcing theory include forcing periodic solutions to second-order Lagrangian systems.
Refreshments at 3:15 p.m. in Room 321 Altgeld Hall

  
Information Protection Seminar,  114 Coordinated Science Lab,  4:30 p.m.
  
Katia Hayati (University of Illinois at Urbana-Champaign)
Random walks in exponential and subexponential DLP methods
  
Abstract: Random walks are perhaps best known from Pollard's rho and kangaroo methods. Recently, however, they have been used in index calculus methods for solving the DLP with very promising results. This talk will briefly survey the rho and kangaroo methods and associated collision finding algorithms, then focus on recent developments by Enge and Gaudry in a subexponential setting.



THURSDAY, NOVEMBER 29

  
Math - Physics (BCDE) Lunch Seminar,  6-110 Engineering Science Bldg,  12:05 p.m.
  
Rajesh Govindan (Chicago)
Brane-Antibrane Inflation
  
Abstract: We show how the motion through extra dimensions of a gas of branes and antibranes can, under certain circumstances, produce an era of inflation as seen by observers trapped on a three-brane, with the inflation being the inter-brane separation. Although most of our discussion refers to arbitrary p-branes, when we need to be specific we assume that they are D-branes of type II or type I string theory. For realistic brane couplings, such as those arising in string theory, the inter-brane potentials are too stepp to inflate the universe for acceptably long times. However, for special regions of the parameter space of brane-antibrane positions the brane motion is slow enough for there to be sufficient inflation. Inflation would be more generic in models where the inter-brane interactions are much weaker. The spectrum of primordial density fluctuations predicted has index n slightly less than 1, and an acceptable amplitude, provided that the extra dimensions have linear size 1/r 1012 GeV. Reheating occurs as in hybrid inflation, with the tachyonic instability of the brane-antibrane system taking over for small separations. The tachyon field can induce a cascade mechanism within which higher-dimension branes annihilate into lower-dimension ones. We argue that such a cascade naturally stops with the production of three-branes in ten-dimensional string theory.

  
Several Complex Variables Seminar,  243 Altgeld Hall,  12:00 p.m.
No meeting this week

  
Analytic and Elementary Number Theory,  243 Altgeld Hall,  1:00 p.m.
No meeting today because of Ono's Colloquium talk

  
Group Theory,  347 Altgeld Hall,  1:00 p.m.
  
Peter Brinkmann (Doob Postdoc)
Morse theory on cell complexes
  
Abstract: I will discuss Morse theory on affine cell complexes as introduced by Bestvina and Brady, as well as applications to finiteness properties of groups

  
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, II
  
Abstract: In connection with the noncommutative martingale Hardy space H1, G. Pisier and Q. Xu introduced the noncommutative martingale BMO and proved that BMO = (H1)*. We will discuss interpolation results (both for the complex and the real method) between noncommutative BMO and noncommutative Lp, where 1 £ p < ¥.

  
Algebraic Geometry Seminar,  347 Altgeld Hall,  2:00 p.m.
  
Tom Zerger (Saginaw Valley State)
Deformations and Contractibility of Reducible Rational Curves with Irreducible Components of Length One in Smooth Complex Threefolds.
  
Abstract: Let C = (union) Ci be a chain of n smooth rational curves with a rational formal neighborhood in a smooth complex threefold X, where each component has length one and intersects the canonical sheaf KX trivially. A formal construction will be utilized to show that if f: X ® Y is an analytic contraction of C with f(C) = q, then a general hyperplane section of q has an An singularity at q. Then, from the theory of deformations of An singularities and their simultaneous resolutions, precise conditions will be given as to when C will deform formally in X and when a formal contraction of C exists. Definitions of what is meant by a formal deformation and formal contraction will be given.

  
Algebraic Number Theory,  241 Altgeld Hall,  2:00 p.m.
  
Thomas Kuhnt (Graduate Student, UIUC)
Topic: TBA

  
Analysis Seminar,  243 Altgeld Hall,  2:00 p.m.
  
Florin Boca (Assistant Professor, UIUC)
Asymptotics for the statistics of a billiard in a square
  
Abstract: I will discuss some results obtained in joint work with R. Gologan and A. Zaharescu, concerning the statistics of a billiard in a modifield square with pockets at the corners and trajectory originating from one corner, when the size of the pocket tends to zero.

  
Knot Theory RAP,  345 Altgeld Hall,  2:00 p.m.
  
John Sullivan (Associate Professor, UIUC)
2-bridge knots and rational tangles (cont.)

  
Commutative Ring Theory Seminar,  243 Altgeld Hall,  3:00 p.m.

  
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.
  
Ken Ono (University of Wisconsin at Madison )
Values of modular functions and divisors of modular forms
  
Abstract: The values and the coefficients of the modular function j(z) play a variety of important roles in number theory and representation theory. For example, its values generate class fields in algebraic number theory, and its coefficients are the degrees of the graded representation of the Monster group. In this lecture I will introduce a specific sequence of modular functions jn whose arithmetic literally dictates the behavior of all modular forms on SL2(Z). The corollaries include: (1) Borcherds type infinite products for generic forms;

(2) Universal recursions for Fourier expansions of all forms;

(3) p-adic class number formulas in number theory.

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


FRIDAY, NOVEMBER 30

  
RAP ``Etale cohomology",  159 Altgeld Hall,  10:00 a.m.
  
Marco Schlichting (Doob Postdoc, UIUC)
Proper base change theorem (cont.)

  
RAP - Conformal invariance, intersection exponents and critical percolation,  145 Altgeld Hall,  4:00 p.m.
  
Robert Bauer (Assistant Professor, UIUC)
Values of Brownian intersection exponents II

  
Model Theory Seminar,  141 Altgeld Hall,  4:00 p.m.
  
Wai Yan Pong (Doob Postdoc, UIUC)
Euler Characteristics and Grothendieck Rings for first order structures
  
Abstract: We will survey a paper by Krajicek and Scanlon in which they show that K0 of the field of complex numbers contains as subring the ring of polynomials over the integers with continuum many variables.

File translated from TEX by TTH, version 2.01.
On 21 Nov 2001, 11:51.