Current Seminars
updated 2/25/2004

   
FEBRUARY 25 - 27, 2004
   
Discrete Mathematics Seminar
Topic: Van der Waerden type problems for 2-dimensional lattices
Presenter:  Jozsef Beck, Rutgers University
Date:  Wednesday, February 25, 2004, Time: 2:30 p.m., Location: Fine Hall 224
Abstract:

For the one-dimensional lattice ("integers") there are only two natural subsets: the intervals and the arithmetic progressions. The case of intervals is usually trivial, and the case of arthmetic progressions is extremely hard. Note that very recently Gowers proved some remarkable upper bounds for the van der Waerden threshold number concerning monochromaric arithmetic progressions. If we restrict ourselves to arithmetic progressions starting from zero, then even the "unbounded discrepancy problem" is unsloved (this is a famous open problem raised by Erdos in the 1930's).
For the 2-dimensional lattice one type of natural subset it the "sublattice," but there are many other natural subsets as well, for example the "set of lattice points contained by a rectangle," or simply the "lattice-set of a rectangle." Instead of a rectangle one can take a circle, or other natural geometric shapes. Here the analogue of Erdoos's "unbounded discrepancy problem" is solved. In my talk I focus on three shapes: rectangles, circles, and hyperbola segments. The proofs combine analytic tools like "Riesz product" with combinatorial considerations.

   
Geometry, Representation, and Moduli Seminar
Topic: Lagrangian tori in K3s and crazy algebraic geometry
Presenter: 

Paul Seidel, University of Chicago

Date:  Wednesday, February 25, 2004, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: Seiberg-Witten theory and random partitions
Presenter:  Nikita Nekrasov, IHES
Date:  Wednesday, February 25, 2004, Time: 4:30 p.m., Location: Fine Hall 314
   
Topology Seminar
Topic: Witten's conjecture and Property P
Presenter: Tom Mrowka, MIT
Date: Thursday, February 26, 2004, Time: 4:30 p.m., Location: Fine Hall 314
   
Algebraic Geometry Seminar *** Please note special date, time, and location
Topic: The algebraic approach to the universality theorem
Presenter:  Ai-Ko Liu, University of California, Berkeley
Date:  Friday, February 27, 2004, Time: 3:00 p.m., Location: Fine Hall 314
Abstract: The talk is about the enumeration of nodal curves on algebraic surfaces based on the algebraic tools developed from Seiberg-Witten theory. We will outline the key argument in the algebraic proof of the following universality theorem: The number of nodal singular curves in a generic $\delta$-dimensional $5\delta-1$-very ample complete linear sub-systems of $|L|$ can be expressed as universal polynomials of charactistic numbers of $L$ and $M$.
   
MARCH 1-5, 2004
   
Analysis Seminar
Topic: Asymptotics for the measure invariant with respect to a diffusion related to $NA$ groups
Presenter: 

Andrzej Hulanicki , Wroclaw University and CUNY

Date:  Monday, March 1, 2004, Time: 4:00 p.m., Location: Fine Hall 314
   
Joint Princeton University/Institute for Advanced Study Number Theory Seminar
Topic:

Congruences Between Stable and Endoscopic Forms and Arithmetic Applications (Work in Progress)

Presenter: 

Michael Harris, Paris and Harvard University

Date:  Monday, March 1, 2004, Time: TBA, Location: IAS
   
PACM Colloquium
Topic:

New developments of nonparametric methods in financial econometrics

Presenter: 

Jianqing Fan, Operations Research and Financial Engineering, Princeton University

Date:  Monday, March 1, 2004, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: This talk gives an overview on the nonparametric techniques that are useful for financial econometric problems. The problems include estimation and inferences of instantaneous returns and volatility functions, time-dependent stochastic models, estimation of transition densities and state price densities. We first briefly describe the problems and then outline main techniques and main results. Some useful probabilistic aspects of diffusion processes are also briefly summarized to facilitate our presentation and applications.
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Jim Bryan, University of British Columbia
Date:  Tuesday, March 2, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Mathematical Physics Seminar
Topic: Conformal restriction properties
Presenter: Wendelin Werner, Universite Paris Sud, Orsay
Date: Tuesday, March 2, 2004, Time: 4:30 p.m., Location: Jadwin A06
Abstract: This talk is based on joint work with Greg Lawler, Oded Schramm, and Roland Friedrich. We will describe the so-called restriction properties and give various equivalent descriptions of the various random sets that do satisfy this property. We will then outline how they are related to the (conjectural) scaling limit of simple two dimensional models, to representation theory and to some aspects of conformal field theory.
   
Discrete Mathematics Seminar
Topic: The intersection of a matroid and a simplicial complex
Presenter:  Eli Berger , Princeton University
Date:  Wednesday, March 3, 2004, Time: 2:30 p.m., Location: Fine Hall 224
Abstract: See http://www.math.princeton.edu/~bsudakov/berger2004.ps
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

Christopher Woodward, Rutgers University

Date:  Wednesday, March 3, 2004, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: Critical phenomena in two dimensions, conformal invariance and Schramm-Loewner Evolutions
Presenter:  Wendelin Werner, Universite Paris Sud, Orsay
Date:  Wednesday, March 3, 2004, Time: 4:30 p.m., Location: Fine Hall 314
   
Ergodic Theory and Statistical Mechanics Seminar
Topic: Reinforced Random Walk
Presenter: 

Michael Keene, Wesleyan University

Date:  Thursday, March 4, 2004, Time: 2:00 p.m., Location: Fine Hall 322
Abstract:

One of the distinguishing properties of the present scientific method is reproducibility.

In one of its guises, probability theory is based on statistical reproduction, near certainty being obtained of truth of statements  by averaging over long term to remove randomness occurring in individual experiments.

When one assumes, as is often the case, that events farther and farther in the past have less and less influence on the present, the probabilistic paradigm is currently well understood and is successful in many scientific and technological applications.

Recently, however, we have come to realize that precisely in these applications important stocahstic processes occur whose present
outcomes are significantly influenced by events in the remote past.

This behaviour is not at all well understood and some of the simplest questions remain today irritatingly beyond reach.

A salient example occurs in the theory of random walks, where there  is a dichotomy between recurrent and transient behaviour.

After explaining this classical dichotomy, we present a very simple example with infinite memory which is neither known to be transient  nor recurrent.

Then, using a reinforcement mechanism due to POLYA, we explain the nature of a particular infinite memory process in terms of spontaneous emergence of opinions.

Finally we would like to discuss briefly some of our recent results towards understanding the recurrence-transience dichotomy for
reinforced random walks, and indicate an application to universal coding used in optical CD technology.

   
Joint Analysis Seminar
Topic: The singular set of 1-1 Integral Currents
Presenter:  Tristan Riviere, ETH
Date:  Thursday, March 4, 2004, Time: 3:30 p.m., Location: Fine Hall 214
   
Topology Seminar
Topic: On classifying simply connected 7-manifolds.
Presenter: Diarmuid J. Crowley, Pennylvania State University
Date: Thursday, March 4, 2004, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: I shall present a program for the classification of simply connected, closed, smooth 7-manifolds.
   
Joint Analysis Seminar *** Please note special time
Topic: Brownian loop soups and conformal field theory
Presenter:  Wendelin Werner, Universite Paris Sud, Orsay
Date:  Thursday, March 4, 2004, Time: 4:45 p.m., Location: Fine Hall 214
   
Geometric Analysis Seminar
Topic: On scalar-flat Kaehler surfaces
Presenter:  Yann Rollin, MIT
Date:  Friday, March 5, 2004, Time: 3:00 p.m., Location: Fine Hall 314
   
MARCH 8-12, 2004
   
PACM Colloquium - Distinguished Lecture Series *** Please note special time and location
Topic:

Time reversal, imaging and communications in richly scattering environments

Presenter:  George Papanicolaou, Department of Mathematics, Stanford University
Date:  Monday, March 8, 2004, Time: 8:00 p.m., Location: A02 McDonnell Hall
Abstract:

Signals received by an array, time reversed and re-emitted into the environment will pack-propagate to the vicinity of the sources that produced them. It is remarkable that the focusing resolution in time reversal is much better in a strongly scattering medium than in a homogeneous one, assuming dissipation is negligible. This interesting phenomenon has many surprising applications in imaging and communications through clutter. I will describe time reversal and its properties, explain mathematically how super-resolution occurs in random media and introduce some imaging methods that deal effectively with clutter. I will also describe how time reversal can be used in communications.

 
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Fabrizio Catanese, Bayreuth
Date:  Tuesday, March 9, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Mathematical Physics Seminar
Topic: Spontaneous symmetry breaking of noncompact sigma models in three dimensions
Presenter: Martin Zirnbauer, Cologne University and the Institute for Advanced Study
Date: Tuesday, March 9, 2004, Time: 4:30 p.m., Location: Jadwin A06
Abstract: Noncompact sigma models constitute the bosonic sector of supersymmetric field theories for single-electron systems with disorder. The Hessian of the action function of a noncompact sigma model turns out to be convex in the full parameter range, which allows convexity methods to be used. By generalizing the Brascamp-Lieb inequality to the case of Riemannian manifolds, we establish free-field bounds on some correlation functions of the sigma model. These bounds imply spontaneous symmetry breaking in three dimensions, and are consistent with the existence of extended states in the disordered electron system. (Joint work with T. Spencer.)
   
Discrete Mathematics Seminar
Topic: TBA
Presenter:  Sang-il Oum, Princeton University
Date:  Wednesday, March 10, 2004, Time: 2:30 p.m., Location: Fine Hall 224
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

Thomas Nevins , University of Michigan

Date:  Wednesday, March 10, 2004, Time: 3:00 p.m., Location: Fine Hall 214
 
Department Colloquium
Topic: TBA
Presenter:  Charlie Fefferman, Princeton University and the Courant Institute
Date:  Wednesday, March 10, 2004, Time: 4:30 p.m., Location: Fine Hall 314
   
Joint Analysis Seminar
Topic: Solving free boundary problems by variational and maximum principle methods
Presenter:  David Jerison, MIT
Date:  Thursday, March 11, 2004, Time: 3:30 p.m., Location: Fine Hall 214
   
Topology Seminar
Topic: New symplectic 4-manifolds with $b_2^+=1$
Presenter: Jongil Park, Konkuk University and Michigan State University
Date: Thursday, March 11, 2004, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: In this talk I'd like to review some symplectic 4-manifolds with $b_2^+=1$ and  I present a new family of simply connected symplectic 4-manifolds with $b_2^+=1$ and $c_1^2=2$ which are not diffeomorphic to rational surfaces. I also address some applications regarding this new symplectic 4-manifolds.
   
Geometric Analysis Seminar
Topic: Energy of solutions of Yamabe type problems and their Morse index
Presenter:  Mohameden Ahmedou, University of Bonn
Date:  Friday, March 12, 2004, Time: 3:00 p.m., Location: Fine Hall 314
   
SPRING BREAK MARCH 13 - 21, 2004
   
MARCH 22 - 26, 2004
   
Joint Princeton University/Institute for Advanced Study Number Theory Seminar
Topic:

TBA

Presenter: 

Abhinav Kumar, Harvard University

Date:  Monday, March 22, 2004, Time: 4:00 p.m., Location: Fine Hall 322
   
PACM Colloquium - Please note special time and location

Lewis-Sigler Topical Seminar Series 2004, Functional Genomics

Topic: Engineered Gene Networks: A Reductionist Approach to Systems Biology
Presenter:  James Collins, Center for BioDynamics, Boston University
Date:  Monday, March 22, 2004, Time: 4:00 p.m., Location: Room 101, Carl Icahn Lab
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Steven Sperber, University of Minnesota and Princeton University
Date:  Tuesday, March 23, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Mathematical Physics Seminar
Topic: Dynamics of magnetic Bloch electrons
Presenter: Herbert Spohn, Zentrum Mathematik and Physics Department, Technical University, Munich
Date: Tuesday, March 23, 2004, Time: 4:30 p.m., Location: Jadwin A06
Abstract: As a standard model of solid state physics we consider independent electrons subject to a periodic lattice potential and a strong uniform magnetic field with rational flux per unit cell. We then explain the first order corrections to the effective Hamiltonian from the Peierls substitution.
   
Discrete Mathematics Seminar
Topic: Analysis of random graph processes using differential equations
Presenter:  Joel Spencer, Courant Institute, NYU
Date:  Wednesday, March 24, 2004, Time: 2:30 p.m., Location: Fine Hall 224
Abstract: See http://www.math.princeton.edu/~bsudakov/spencer2004.ps
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

Michael Shapiro, Michigan State University

Date:  Wednesday, March 24, 2004, Time: 3:00 p.m., Location: Fine Hall 214
   
MARCH 29 - APRIL 2, 2004
   
PACM Colloquium
Topic:

Upper bounds on coarsening rates

Presenter: 

Robert Kohn, Courant Institute of Mathematics, New York University

Date:  Monday, March 29, 2004, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: I will discuss surface-energy-driven coarsening of two-phase microstructures. Such coarsening is observed in many physical systems; two basic examples are motion by surface diffusion and Mullins-Sekerka (evaporation-condensation) dynamics. Experiments and simulations suggest that solutions are in some sense statistically self-similar. There is, however, virtually nothing known with mathematical rigor. I will briefly introduce this topic, then present recent joint work with Felix Otto (Comm. Math. Phys. 2002). Our main accomplishment is an upper bound on the coarsening rate, consistent with the conjectured self-similar behavior. Our work is also interesting for its viewpoint, which is new and potentially applicable to many other problems. I will close with one such application, to epitaxial growth -- joint work with Xiaodong Yan (Comm. Pure Appl. Math. 2003).
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Jun-Muk Hwang, KIAS and Harvard University
Date:  Tuesday, March 30, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Mathematical Physics Seminar
Topic: Ferromagnetism in the Hubbard model --- a constructive approach
Presenter: H. Tasaki, Gakushuin University
Date: Tuesday, March 30, 2004, Time: 4:30 p.m., Location: Jadwin A06
Abstract: It is believed that strong ferromagnetic order in some solids is generated by a subtle interplay between quantum many-body effects and the spin-independent Coulomb interactions between electrons.  I will describe our constructive approach to ferromagnetism in the Hubbard model, which is a standard idealized model for strongly interacting electrons in a solid.  I present nonsingular models of itinerant electrons with only spin-independent interactions where the low energy behavior is proved to be that of a ``healthy'' ferromagnetic insulator.  I will also discuss some open problems and conjectures regarding metallic ferromagnetism.
   
Discrete Mathematics Seminar
Topic: TBA
Presenter:  Doron Zeilberger, Rutgers University
Date:  Wednesday, March 31, 2004, Time: 2:30 p.m., Location: Fine Hall 224
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

C. C. Liu, Harvard University

Date:  Wednesday, March 31, 2004, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: TBA
Presenter:  Maciej Zworski, University of California, Berkeley
Date:  Wednesday, March 31, 2004, Time: 4:30 p.m., Location: Fine Hall 314
   
Ergodic Theory and Statistical Mechanics Seminar
Topic: Dense random regular graphs: Methods and challenges
Presenter: 

Benjamin Sudakov, Princeton University

Date:  Thursday, April 1, 2004, Time: 2:00 p.m., Location: Fine Hall 322
Abstract: Properties of random $d$-regular graphs were studied extensively starting with late 70's. But until very recently almost all the results were obtained for graphs whose degree $d$ is relatively small compared to the number of vertices $n$. In this talk we survey various results for dense random regular graphs which were obtained in the last few yeas. We will focus on the new approaches which were used and discuss some interesting questions which are still open.
   
Joint Analysis Seminar
Topic: TBA
Presenter:  Maciej Zworski, University of California, Berkeley
Date:  Thursday, April 1, 2004, Time: 3:30 p.m., Location: Fine Hall 214
   
APRIL 5- APRIL 9, 2004
   
PACM Colloquium
Topic: Efficient high-order methods for acoustic and electromagnetic scattering simulations
Presenter:  Fernando Reitich, University of Minnesota
Date:  Monday, April 5, 2004, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: In this talk we will present a variety of techniques for the solution of electromagnetic and acoustic scattering problems that are aimed at overcoming the limitations of state-of-the-art scattering solvers. We will begin with a brief review of the techniques most commonly used for the numerical simulation of scattering experiments, highlighting their advantages and shortcomings. In addition to providing a context for the presentation, the review will motivate the continued need for algorithms that can tackle these problems efficiently without sacrificing accuracy and error-controllability. In this connection, we shall first discuss some theoretical considerations that lead to a class of efficient, high-order perturbative methods that are particularly well-suited for rough-surface scattering (e.g. ocean surfaces, diffraction gratings, etc). We shall further explain how these algorithms can be used to resolve the scattering off multi-scale surfaces, leading to consideration of high-frequency problems. With regard to the latter, we shall next present the main ideas behind our recent design of a technique for the solution of the integral-equation formulation of the scattering problem in the high-frequency regime. As we will show, our scheme can deliver error-controllable answers without the need to discretize on the scale of the wavelength of radiation, and it therefore holds significant promise for applicability in a variety configurations (e.g. military vehicles illuminated with centimeter, or even millimeter, waves). Finally, as we shall explain, our high-frequency strategy possesses the additional property that it continuously reduces to a full discretization of the integral equations as the frequency is decreased to a moderate regime. In this regard, and if time permits, we will also present an innovative technique for the efficient solution of the (singular) integral-equations pertaining to volumetric scattering up to these moderate frequencies, that can exhibit arbitrarily large, tunable orders of convergence.
   
Algebraic Geometry Seminar
Topic: Varieties with ample cotangent bundle
Presenter:  Olivier Debarre, Strasbourg
Date:  Tuesday, April 6, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Discrete Mathematics Seminar
Topic: TBA
Presenter:  Michael Krivelevich, Tel Aviv University
Date:  Wednesday, April 7, 2004, Time: 2:30 p.m., Location: Fine Hall 224
   
APRIL 12- APRIL 16, 2004
   
Joint Princeton University/Institute for Advanced Study Number Theory Seminar
Topic:

TBA

Presenter: 

Zhengyu Mao, Rutgers University - Newark 

Date:  Monday, April 12, 2004, Time: 4:00 p.m., Location: Fine Hall 322
   
PACM Colloquium
Topic:

Vorticity and Wave Confinement A Rotationally Invariant Limiter Approach to Modeling Small Scales

Presenter:  John Steinhoff, University of Tennessee Space Institute
Date:  Monday, April 12, 2004, Time: 4:00 p.m., Location: Fine Hall 214
Abstract:

A new computational method, Vorticity/Wave Confinement, (V/WC), is described. V/WC has been shown to efficiently treat thin features in complex fluid flow and time domain wave equation problems involving vortices and acoustic pulses. The method allows them to be propagated over arbitrarily long distances with no spreading due to numerical errors. It has also been shown to be effective in representing boundary layers on surfaces as thin vortical layers “immersed” in uniform Cartesian grids. We define these thin vortical or wave regions as “features.” Outside these features, where the flow is irrotational or the wave amplitude vanishes, the method automatically reduces to a conventional finite difference approximation to the correct continuum partial differential equation (pde). The features are treated as a type of weak solution and, within the features, a nonlinear difference equation, as opposed to finite difference approximation, is solved that does not necessarily represent a Taylor expansion discretization of a simple pde. The approach is similar to artificial compression and shock capturing schemes, where conservation laws are satisfied across discontinuities. For propagating features, the result of this conservation is that integral quantities such as total momentum and amplitude, and centroid motion are accurately computed. Effectively, the features are treated as multi-dimensional nonlinear discrete solitary waves that “live” on the computational lattice. These obey a “confinement” relation that is a generalization to multiple dimensions of 1-D discontinuity capturing schemes. A major point is that the method involves a rotationally invariant limiter – a single limiter that is a function of rotationally invariant variables. This is in contrast to conventional discontinuity capturing schemes which may involve a concatenation of separate 1-D limiters, each a function of variables along each axis.

Results will be shown for convection of thin convecting vortex filaments, flow over complex surfaces “immersed” in uniform grids, and thin acoustic pulses scattering from complex surfaces.

   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Ravi Vakil, Stanford University
Date:  Tuesday, April 13, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Discrete Mathematics Seminar
Topic: TBA
Presenter:  Van Vu , University of California, San Diego
Date:  Wednesday, April 14, 2004, Time: 2:30 p.m., Location: Fine Hall 224
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

Alexander Braverman, Brown University

Date:  Wednesday, April 14, 2004, Time: 3:00 p.m., Location: Fine Hall 214
   
APRIL 19 - APRIL 23, 2004
   
Joint Princeton University/Institute for Advanced Study Number Theory Seminar
Topic:

TBA

Presenter: 

Harald Helfgott, Yale University

Date:  Monday, April 19, 2004, Time: 4:00 p.m., Location: Fine Hall 322
   
PACM Colloquium
Topic:

TBA

Presenter: 

Nicholas J. Pippenger, Computer Science, Princeton University

Date:  Monday, April 19, 2004, Time: 4:00 p.m., Location: Fine Hall 214
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Mikhail Kapranov, Yale University
Date:  Tuesday, April 20, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
APRIL 26 - APRIL 30, 2004
   
Joint Princeton University/Institute for Advanced Study Number Theory Seminar
Topic:

TBA

Presenter: 

Ben Brubaker, Stanford University

Date:  Monday, April 26, 2004, Time: 4:00 p.m., Location: Fine Hall 322
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Jaroslaw Wisniewski, Purdue University and Warsaw
Date:  Tuesday, April 27, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
MAY 3 - MAY 7, 2004
   
Algebraic Geometry Seminar
Topic: TBA
Presenter:  Joe Harris, Harvard University
Date:  Tuesday, May 4, 2004, Time: 4:30 p.m., Location: Fine Hall 322
   
Geometry, Representation, and Moduli Seminar
Topic: TBA
Presenter: 

Alexander Braverman, Brown University

Date:  Wednesday, May 5, 2004, Time: 3:00 p.m., Location: Fine Hall 214