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Past schedules:August|
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FALL 2009 Seminars Schedule
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Mondays
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Analysis Seminar
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Time: 4:00-5:00pm *
Location: Cupples I, Room 199
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Host: Prof. Richard Rochberg
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Tuesdays
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Combinatorics Seminar
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Time: 2:00-3:00pm *
Location: Cupples I, Room 199
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Host: Russ Woodroofe
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Graduate Organized Talks Seminar
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Time: 4:00-5:00pm *
Location: Cupples I, Room 199
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Host: Raphiel Murden
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Wednesdays
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Graduate Students Talk
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Time: 3:00-4:00pm *
Location: Cupples I, Room 199
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Host: Prof. Guido Weiss
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Algebraic Geometry Seminar
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Time: 4:00-5:30pm *
Location: Cupples I, Room 215
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Host: Prof. Mohan Kumar
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Thursdays
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Geometry and Topology Seminar
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Time: 3:00-4:00pm *
Location: Cupples I, Room 111
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Host: Prof. Xiang Tang
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Fridays
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Wavelet Seminar
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Time: 3:30-4:30pm *
Location: Cupples I, Room 199
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Host: Prof. Guido Weiss
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* Times may vary, please consult the schedule below for details:
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OCTOBER 2009
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Thursday, October 1
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Geometry and Topology Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 111
Host: Prof. Xiang Tang
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Speaker: Liwei Chen
Department of Mathematics, Washington University in St. Louis
Title: An Introduction to Morse Homology
Abstract: In this talk, I give a definition of Morse homology by outlining the basic ideas and showing some examples.
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Tuesday, October 6
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Combinatorics Seminar
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Time: 2:00-3:00pm
Location: Cupples I, Room 199
Host: Russ Woodroofe
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Speaker: Joe Bohanon
Department of Mathematics, Washington University in St. Louis
Title: The Brauer-Fowler Theorem
Abstract: he Brauer-Fowler Theorem states that any group G of even order
and size greater than 2 has a subgroup H such that |G|<=|H|^3. This
result is one of the starting points of the Classification of Finite
Simple Groups. I'll discuss how to prove it and some applications.
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Thursday, October 8
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Geometry and Topology Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 111
Host: Prof. Xiang Tang
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Speaker: Liwei Chen
Department of Mathematics, Washington University in St. Louis
Title: An Introduction to Morse Homology, Part II
Abstract: I will give a proof for the isomorphism between Morse homology
and Singular homology.
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Friday, October 9
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Wavelet Seminar
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Time: 3:30-4:30pm
Location: Cupples I, Room 199
Host: Prof. Guido Weiss
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Speaker: Joe Lakey
Department of Mathematics, Washington University in St. Louis
Title: Sampling in principle shift invariant spaces
Abstract: The Shannon sampling theorem says that elements of the
Paley-Wiener space of square-integrable functions bandlimited to a unit
interval can be expressed as sums of their integer samples interpolated by
shifted sinc functions.
This minor miracle relies on the fact that the sinc function has an
interpolation property: its value at the origin is one and its value at
all other integers is zero, and that the sinc function is orthogonal to
its integer shifts.
The miracle is tempered by the fact that the sinc function has lousy
decay, so a lot of samples are needed to approximate a bandlimited
function at any given point. Membership in the Paley-Wiener space is a
physical property, but so is membership in other shift invariant spaces.
Does such a space also admit a "sampling formula"?
This talk will discuss some work done in the past 10 years that has
sought, in part, to provide conditions under which the answer to this
question is "yes" but has also sought descriptions of when one sampling
formula is better than another. Some of this is joint work with Jeff
Hogan.
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Monday, October 12
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Analysis Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Richard Rochberg
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Speaker: Al Baernstein
Department of Mathematics, Washington University in St. Louis
Title: Monotonicity and comparison theorems for certain pde's, with
application to conformal invariants
Abstract: TBA
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Wednesday, October 14
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Lecture
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Time: 10:00-11:30am
Location: Eads, Room 003
Host: Prof. Steven Krantz
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Speaker: Lance Carnes
CEO of PC-TeX
Title: LaTeX in Short Order
Authors: Heike Hofmann, Di Cook, and the ISU Statistical Graphics group
Note:It is best (though not compulsory) for participants to
bring a notebook computer with some form of TeX installed.
We have a site license for PC-TeX, and Steven Xiao can
tell you how to install it.
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Wednesday, October 14
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Lecture
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Time: 2:30-4:00pm
Location: Eads, Room 013
Host: Prof. Steven Krantz
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Speaker: Lance Carnes
CEO of PC-TeX
Title: LaTeX in Short Order
Authors: Heike Hofmann, Di Cook, and the ISU Statistical Graphics group
Note:It is best (though not compulsory) for participants to
bring a notebook computer with some form of TeX installed.
We have a site license for PC-TeX, and Steven Xiao can
tell you how to install it.
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Wednesday, October 14
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Graduate Students Talk
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Time: 3:00-4:00pm
Location: Cupples I, Room 199
Host: Prof. Guido Weiss
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Speaker: Russ Woodroofe
Department of Mathematics, Washington University in St. Louis
Title: Three views of the Moebius function
Abstract: I will start by discussing the classic Moebius function and the
technique of Moebius
inversion in number theory. I will then show how to extend the Moebius
function and inversion
technique to any partially ordered set. I will finish by relating the
Moebius function to the
topology of a related simplicial complex.
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Thursday, October 15
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Geometry and Topology Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 111
Host: Prof. Xiang Tang
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Speaker: Liwei Chen
Department of Mathematics, Washington University in St. Louis
Title: An Introduction to Morse Homology 3
Abstract: I will finish the proof for the isomorphism between Morse
homology and Singular homology. After that I will give an application. If
there is time left, I will begin to talk about the invariance of Morse
homology.
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Thursday, October 15
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Nan Lin
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Speaker: Professor Dianne Cook
Department of Statistics, Iowa State University
Title: Statistical Inference for Visual Methods
Abstract:People can have difficulty understanding randomness. They can often
see patterns in plots of data. Beginning
statistics students have great difficulty interpreting residual plots,
often reporting patterns that are quite commonly seen by chance. Oft-
times when we listen to a speaker explaining what they see in a plot
we might dispute their interpretation. Plots of data tend to provoke
a response of: "Is what we see really there?''
Disagreements aside, plots are a vital part of data analysis. Model
diagnosis is dependent on plots. Exploratory data analysis is a plot-
rich endeavor. Statistical graphics might lack the rigor of
inferential methods, but rigidly adhering to inferential protocols
prevents us from discovering something new. While it is completely
invalid to look at data and then pursue hypothesis testing, not to
look at data and miss a feature invalidating inference would be
equally stupid. Despite more than a century of active research, the
role for graphics in statistics is still a subject of active debate
among statisticians. The lack of a formal framework contributes to
this continuing debate.
In this talk we will discuss ways to give visual statistical methods
an inferential framework. Statistical significance of
"discoveries'' is measured by having the human viewer compare the plot
of the real dataset with collections of plots of null datasets: plots
take on the role of test statistics, and human cognition the role of
statistical tests. This is a simple but rigorous protocol that
provides inferential validity modeled after the "lineup'', popular
from criminal legal procedures. Another protocol modeled after the
"Rorschach'' inkblot test well-known from (pop-)psychology will help
analysts acclimatize to random variability before being exposed to the
plot of the real data. Researchers accustomed to clinical trials might
be comfortable with these new protocols, and teachers of statistics
might find they can help students obtain years of data analysis
experience within a shorter time period.
Joint work with Andreas Buja, Heike Hofmann, Michael Lawrence, Eun-kyung
Lee, Deborah F. Swayne, Hadley Wickham
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Tuesday, October 20
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Graduate Organized Talks Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Raphiel Murden
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Speaker: Nic Sedlock
Department of Mathematics, Washington University in St. Louis
Title: Analytic Function Spaces and
Why I Love Them
Abstract: I will talk about analytic function spaces, and the
connections between thinking of them as sets of functions and as
Banach spaces, mainly concentrating on spaces similar to the Hardy
space.
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Wednesday, October 21
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Algebraic Geometry Seminar
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Time: 4:00-5:30pm
Location: Cupples I, Room 215
Host: Prof. Mohan Kumar
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Speaker: Professor Arno Van den Essen
Department of Mathematics, Washington University in St. Louis
Title: The Amazing Image Conjecture
Abstract: TBA
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Wednesday, October 21
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Graduate Students Talk
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Guido Weiss
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Speaker: Rajan Mehta
Department of Mathematics, Washington University in St. Louis
Title: What is a (super)representation of a Lie group(oid)?
Abstract: Lie groupoids are a generalization of Lie groups that incorporate both
"internal" and
"external" symmetries. Representation theory is a valuable tool for studying
Lie groups,
so it would be nice to similarly utilize representation theory in the study
of Lie
groupoids. There is a reasonably natural definition of Lie groupoid
representation, but
it unfortunately fails to include an adjoint representation. However, it
turns out that
this problem can be avoided if we allow for a more general notion of a
superrepresentation.
First, I will explain what a Lie groupoid is, give some concrete examples,
and illustrate
the problem one encounters in trying to define an adjoint representation.
Next, I will
describe how the definition of a representation of a Lie group can be
restated in the
language of homological algebra. In this point of view, the definition of
superrepresentation is straightforward, and the result can be translated
back into
conventional language. In the case of Lie groupoids, we can define "adjoint
superrepresentations". I'll end with a simple example related to the
geometry of the
sphere.
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Thursday, October 22
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Geometry and Topology Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 111
Host: Prof. Xiang Tang
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Speaker: Liwei Chen
Department of Mathematics, Washington University in St. Louis
Title: An Introduction to Morse Homology 4
Abstract: I will talk about the topological invariance of Morse homology.
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Thursday, October 22
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Nan Lin
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Speaker: Professor Tiejun Tong
Department of Applied Mathematics, University of Colorado at Boulder
Title: Improved mean estimation for high-dimensional data and its application to diagonal discriminant analysis
Abstract: High-dimensional data such as microarrays have created new challenges to
traditional statistical methods. In particular, the standard estimates of the mean vector
are usually unreliable when the number of samples is small. To address this problem, we
propose a family of shrinkage estimators for the mean vector under the assumptions of
unequal and unknown variances. We show that the proposed estimators are minimax and
thus dominate the sample mean under the quadratic loss function. The proposed method
is general and widely applicable, whereas we illustrate its usefulness in the framework
of discriminant analysis. Speci¯cally, we propose a shrinkage-based diagonal discrimi-
nant rule and demonstrate its improvement over the original competitor through both
simulations and real data analysis.
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Friday, October 23
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Wavelet Seminar
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Time: 3:30-4:30pm
Location: Cupples I, Room 199
Host: Prof. Guido Weiss
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Speaker: Professor Ed Wilson
Department of Mathematics, Washington University in St. Louis
Title: Generalizations of Sampling Functions
Abstract: The theory of sampling functions (as discussed in the recent
Wavelet Seminar talk by
Joe Lakey) has several interesting generalizations. We will begin with a
format for the
material discussed by Joe for scaling functions on the real line, then
quickly indicate how this
format is easily adapted to the context of lattice subgroups in a locally
compact abelian group.
We will then show how the format naturally carries over to sampling
functions associated with
certain non-abelian groups and to sampling functions associated with regular
actions of a
discrete abelian group on a measure space. These generalizations are of
particular interest in
composite wavelet theory and for the study of dilation actions of various
discrete abelian
affine groups.
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Monday, October 26
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Analysis Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Richard Rochberg
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Speaker: Professor Xiang Tang
Department of Mathematics, Washington University in St. Louis
Title: Mackey's machine and duality of gerbes
Abstract: I will start with reviewing Mackey's machine about
representations of finite groups. I will explain how to use this
approach to obtain some interesting geometry results.
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Tuesday, October 27
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Combinatorics Seminar
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Time: 2:00-3:00pm
Location: Cupples I, Room 199
Host: Russ Woodroofe
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Speaker: Professor John Shareshian
Department of Mathematics, Washington University in St. Louis
Title: Intervals in subgroup lattices of finite groups
Abstract: Motivated by a problem from universal algebra, group theorists
have attempted for some time to settle the question of whether for every
finite lattice L, there exist a finite group G and a subgroup H of G such
that the lattice of subgroups of G containing H is isomorphic to L.
Although
a negative answer is expected, the question remains open. I will discuss
the general ideas from finite group theory that have been used to study
this
question and explain the so far persistent obstacles to a solution.
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Tuesday, October 27
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Graduate Organized Talks Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Raphiel Murden
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Speaker: Mike Deutsch
Department of Mathematics, Washington University in St. Louis
Title: Variations on a theme of Goursat
Abstract: Geometrically, an element of SO3(R) is just a rotation of R^3
about some line through the origin by some angle \theta. Useful, but
hardly exciting. During his study of minimal surfaces, Goursat was led to
consider the group SO3(C). Does it have a geometric description analogous
to that of SO3(R)? In this painfully elementary talk, we will present
Goursat's answer to this question and present a new connection to minimal
surface theory.
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Wednesday, October 28
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Algebraic Geometry Seminar
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Time: 4:00-5:30pm
Location: Cupples I, Room 215
Host: Prof. Mohan Kumar
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Speaker: Professor Arno Van den Essen
Department of Mathematics, Washington University in St. Louis
Title: The Amazing Image Conjecture
Abstract: Continuation of last week's seminar.
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NOVEMBER 2009
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Monday, November 2
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Analysis Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Richard Rochberg
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Speaker: Professor Marcus Carlsson
Department of Mathematics, Purdue University
Title: Approximation of functions by sums of (few) exponentials and
AAK-theory for Hankel operators
Abstract: An algorithm from 2004 by G. Beylkin and L. Monzon aimed at
achieving the first part of the title, is shown to be a consequence
of the
Adamyan Arov Krein theorem on finite rank approximations of Hankel
operators, (at least for certain cases). The algorithm does however
work
in greater generality than the current theory supports. I will
introduce
various operators that in one way or another deserves the name Hankel
operator, present new results about these as well as open problems.
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Tuesday, November 3
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Graduate Organized Talks Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Raphiel Murden
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Speaker: Ben Manning
Department of Mathematics, Washington University in St. Louis
Title: TBA
Abstract: Some stuff about wavelets. If there is time, I might prove a theorem.
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Wednesday, November 4
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Roya Beheshti-Zavareh
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Speaker: Professor Dragos Oprea
Department of Mathematics, University of California, San Diego
Title: Generalized theta functions
Abstract: For any compact Riemann surface, we can associate an algebraic
torus, the Jacobian, together with a theta divisor given by the zero locus
of an explicit function, the theta function. In higher rank and over an
arbitrary base, one obtains theta divisors and generalized theta functions
over moduli spaces of vector bundles. I will explain recent results
concerning the spaces of generalized theta functions.
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Friday, November 6
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Wavelet Seminar
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Time: 3:30-4:30pm
Location: Cupples I, Room 199
Host: Prof. Guido Weiss
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Speaker: Professor Hrvoje Sikic
Department of Mathematics, University of Zagreb, Croatia
Title: Systems of translates
Abstract: The study of systems of translates comes
naturally within the general wavelet framework. It
provides, among other things, an interesting connection
between harmonic and functional analysis. Working
with several people from the (world wide) St.Louis
group we have solved some and encountered some
more interesting problems.
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Monday, November 9
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Analysis Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Richard Rochberg
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Speaker: Professor Jeremy Chapman
Department of Mathematics, University of Missouri, Columbia
Title: K-point configurations in vector spaces over finite fields
Abstract: Click here
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Thursday, November 12
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Geometry and Topology Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 111
Host: Prof. Xiang Tang
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Speaker: Philip Huling
Department of Mathematics, Saint-Louis University
Title: Rigidity of Hyperbolic 3-Orbifolds
Abstract: We define a hyperbolic $n$-orbifold to be the quotient of hyperbolic
$n$-space, ${\mathbb H}^n$, by a discrete subgroup, $\Gamma$, of
$\text{Isom}({\mathbb H}^n)$. If $\Gamma$ is cofinite in $\text{Isom}
({\mathbb H}^3)$, then the size of its deformation space (up to conjugation)
is well known. However, we may view $\Gamma$ as being a subset of $\text
{Isom}({\mathbb H}^4)$ to investigate how this inclusion into a higher
dimension allows for more deformations in the group. We find the dimension
of the deformation space of a large class of cofinite Coxeter groups and
then develop tools to analyze the deformation space of groups commensurable
with them. Specifically, we are able to describe the deformation spaces of
those Bianchi groups which have a finite index Coxeter subgroup.
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Thursday, November 19
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Nan Lin
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Speaker: Professor Yuhong Yang
School of Statistics, University of Minnesota
Title: Combining Quantile Regression Estimators
Abstract: Model selection for quantile regression is often a challenging problem.
In addition to the well-known general difficulty of model selection
uncertainty, when
quantiles at multiple probability levels are of interest, typically a single
candidate does not serve all of them well simultaneously. In this talk
we propose methods
to combine quantile estimators. Oracle inequalities show that at each
given probability level, the combined estimators automatically perform
nearly as well as the best candidate. Simulation and real examples
show that the proposed model combination approach often leads to a
substantial gain in accuracy under global
measures of performance. (The talk is based on joint work with Kejia Shan.)
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Monday, November 23
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Analysis Seminar
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Time: 4:00-5:00pm
Location: Cupples I, Room 199
Host: Prof. Richard Rochberg
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Speaker: Jeff Langford
Department of Mathematics, Washington University in St. Louis
Title: TBA
Abstract: TBA
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DECEMBER 2009
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Thursday, December 3, 2009
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Hosts: Prof. David Wright
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Speaker: Professor Arno van den Essen
Department of Mathematics, University of Nijmegen
Title: A Journey through Magic Squares
Abstract: Magic squares are one of the oldest mathematical objects. Found in various cultures, they have been studied by mathematicians
and laymen for over five thousand years.
In this lecture we will take a journey through the extensive
history of these squares: We will discuss normal magic squares,
pan magic squares, prime magic squares, alpha-magic squares, and
Benjamin Franklin's magic squares. We will give special attention to a
method for constructing Franklin's squares that led to a magic square craze in the Netherlands in 2007.
The lecture is aimed at a general mathematical audience. All students are encouraged to attend.
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SPRING 2010 Seminars Schedule
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APRIL 2010
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Thursday, April 8, 2010
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Hosts: Prof. Quo-Shin Chi
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Speaker: Professor Yng-Ing Lee
Department of Mathematics, National Taiwan University
Title: TBA
Abstract: TBA
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Wednesday, April 14, 2010
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Colloquium
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Time: 4:00-5:00pm
Location: TBA
Hosts: Profs. David Wright, Ken Kelton, Ram Cowsik
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Speaker: Professor Srinivasa Varadhan
Courant Institute of Mathematical Sciences, New York University
Title: TBA
Abstract: TBA
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Thursday, April 15, 2010
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Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Al Baernstein
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Speaker: Professor Terry Sheil-Small
Department of Mathematics, University of York, England
Title: TBA
Abstract: TBA
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Thursday, April 22, 2010
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Loeb Undergraduate Lecture in Mathematics
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: TBA
Host: Prof. Ronald Freiwald
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Speaker: Professor Martin Golubitsky
Department of Mathematics and Director of the Mathematical
Biosciences Institute, Ohio State University
Title: Symmetries and Animal Gaits
Abstract: Many gaits of four-legged animals can be described by
spatio- temporal symmetries. For example, when a horse paces it moves
both left legs in unison and then both right legs and so on. The
motion is
described by two symmetries: Interchange front and back legs, and
swap left and right legs with a half-period phase shift.
Biologists postulate the existence of a central pattern generator
(CPG) in the
neuronal system that sends periodic signals to the legs. CPGs can
be thought of as electrical circuits that produce periodic signals
and can be modeled by coupled systems of differential equations
with
symmetries based on leg permutation. In this lecture we discuss
animal gaits; describe how periodic solutions with prescribed spatio-
temporal symmetry can be formed in symmetric systems; construct a
CPG
architecture that naturally produces quadrupedal gait rhythms; and
make several testable predictions about gaits.
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Thursday, April 29, 2010
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Roever Colloquium
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Time: Tea: 4:00-4:30pm
Talk: 4:30-5:30pm
Location: Cupples I, Room 199
Host: Prof. Quo-Shin Chi
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Speaker: Professor Simon Brendle
Department of Mathematics, Stanford University
Title: TBA
Abstract: TBA
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Friday, April 30, 2010
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Roever Seminar
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Time: 3:00-4:00pm
Location: Cupples I, Room 199
Host: Prof. Quo-Shin Chi
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Speaker: Professor Simon Brendle
Department of Mathematics, Stanford University
Title: TBA
Abstract: TBA
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