SEMINARS
Updated: 3-15-2006
 
MARCH 15 -17, 2006
 
"What is Happening in Fine Hall" Seminar
Topic: Conformal invariants associated with a measure
Presenter: Alice Chang, Princeton University
Date:  Wednesday, March 15, 2006, Time: 12:30 p.m., Location: Fine Hall PL
   
Number Theory Seminar
Topic: Freeman Dyson's "Challenge for the Future": The mock theta functions
Presenter: Kathrin Bringmann, University of Wisconsin at Madison
Date:  Wednesday, March 15, 2006, Time: 2:00 p.m., Location: Fine 314
Abstract:

In his last letter to Hardy, Ramanujan defined 17 peculiar functions which are now referred to as his mock theta functions. Although these mysterious functions have been investigated by many mathematicians over the years, many of their most basic properties remain unknown. This inspired Freeman Dyson to proclaim:

"The mock theta-functions give us tantalizing hints of a grand synthesis still to be discovered. Somehow it should be possible to build them into a coherent group-theoretical structure, analogous to the structure of modular forms which Hecke built around the old theta-functions of Jacobi. This remains a challenge for the future."
- Freeman Dyson 1987, Ramanujan Centenary Conference

Here we announce a solution to Dyson's "challenge for the future" by providing the "coherent group-theoretical structure" that Dyson desired in his plenary address at the 1987 Ramanujan Centenary Conference.

In joint work with Ken Ono, we show that Ramanujan's mock theta functions, as well a natural generalized infinite class of mock theta functions may be completed to obtain Maass forms, a special class of modular forms. We then use these results to prove theorems about Dyson's partition ranks. In particular, we shall prove the 1966 Andrews-Dragonette Conjecture, whose history dates to Ramanujan's last letter to Hardy, and we shall also prove that Dyson's ranks `explain' Ramanujan's partition congruences in an unexpected way.

 
Discrete Mathematics Seminar
Topic: First order definability of graphs
Presenter: Oleg Pikhurko, Carnegie Mellon University
Date:  Wednesday, March 15, 2006, Time: 2:15 p.m., Location: Fine 224
Abstract: See http://www.math.princeton.edu/~bsudakov/pikhurko2005-2006.pdf
   
Geometry, Representation Theory, and Moduli Seminar
Topic: Algebraic cobordism
Presenter: Rahul Pandharipande, Princeton University
Date:  Wednesday, March 15, 2006, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: Dispersive Waves Dynamics and Scattering
Presenter: Avraham Soffer, Rutgers University
Date:  Wednesday, March 15, 2006, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: Dispersive wave equations appear naturally as evolution equations in Mathematical-Physics, such as the Schroedinger and Maxwell equations. From a mathematical standpoint they pose a great challenge and a source for many problems in analysis. I will describe some new progress and conjectures about nonlinear equations, and some possible new paradigms.
   
Operation Research and Financial Engineering Seminar
Topic:

Population Monte Carlo and a New Idea Using Data Reinforcement

Presenter: Xiaoxian Luo, Yale University
Date:  Wednesday, March 15, 2006, Time: 4:30 p.m., Location: Room E-219, Engineering Quad
Abstract: Population Monte Carlo (PMC) is an iterated importance sampling and resampling scheme that repeatedly simulates a population of N individuals approximately distributed from a target distribution. The PMC method also has the virtue that the proposal distribution can be adapted to the target distribution along iterations. This is an advantage over MCMC methods: Because the theoretical properties of PMC are derived from importance sampling, the proposal distribution may be adapted freely without the concerns over preserving the Markov property that hinder adaptation in MCMC methods.  Although the original PMC method has established theoretical properties under certain regularity conditions, a closer look shows that it can perform unsatisfactorily, for example, when the target distribution has well separated modes, especially in high dimensions. We propose a new method using an idea of reinforcement to give a different way of making proposals and resampling them.  The performance of the new method is more accurate at each iteration, and more stable over iterations. Theoretical properties can also be established for the new method, and the existing adaptation schemes proposed for the original method can also be embedded in the new method, where they produce better asymptotics. The new method and the original method are compared over several simulated examples and a real statistical problem.
   
Analysis Seminar
Topic: Convergence of trigonometric series
Presenter: Sergey Tikhonov, Centre de Recerca Matematica
Date:  Thursday, March 16, 2006, Time: 4:00 p.m., Location: Fine Hall 322
Abstract: We discuss three new convergence criteria (for p=\infty, 1<p<\infty, and p=1) of belonging of sums of trigonometric series to L_p. One-dimensional and multi-dimensional cases are examined. We also study Hardy-Littlewood type theorem for multiple trigonometric and Walsh series in L_p with Muckenhoupt-type weights.
   
Operation Research and Financial Engineering Seminar ***Please note special date and time
Topic:

Stochastic modeling and inference in nano-scale biophysics

Presenter: Samuel Kou, Harvard University
Date:  Thursday, March 16, 2006, Time: 11:30 a.m., Location: Room E-219, Engineering Quad
Abstract: Recent advances in nanotechnology allow scientists to follow a biological process on a single molecule basis. These advances also raise many challenging stochastic modeling and statistical inference problems. First, by zooming in on single molecules, recent nano-scale experiments reveal that some classical stochastic models derived from oversimplified assumptions are no longer valid. Second, the stochastic nature of the experimental data and the presence of latent processes much complicate the statistical inference. In this talk we will use the modeling of subdiffusion phenomenon in enzymatic conformational fluctuation and the inference of DNA hairpin kinetics to illustrate the statistical and probabilistic challenges in single-molecule biophysics.


Based on joint works with Sunney Xie at Harvard Chemistry Department
   
Geometric Analysis Seminar
Topic: Q-curvature functions on Ricci flat manifolds of dimension 4
Presenter: Xingwang Xu, National University of Singapore
Date:  Friday, March 17, 2006, Time: 3:00 p.m., Location: Fine Hall 314
   
MARCH 20 -25, 2006
   
Algebraic Geometry Seminar
Topic: Rational curves and characterizations of projective varieties
Presenter: C. Araujo, IMPA
Date:  Tuesday, March 21, 2006, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: Projective varieties having rational curves through every point form an important class of varieties from the point of view of classification. These are the so called uniruled varieties. A good way of understanding the geometry of a given uniruled variety is to isolate and study a covering family of rational curves on it. This is especially efficient if the curves from this family have minimal degree with respect to some ample line bundle. Many special projective varieties, such as projective spaces, hyperquadrics, Grassmannians, etc, may be characterized by the behavior of their rational curves of minimal degree. On the other hand, consider the product of projective spaces. In this case, studying only one family of rational curves of minimal degree (the family of lines coming from one of the factors) is not enough to recover all the geometry of the variety. We must study the families of lines coming from all the factors simultaneously. In this talk I will explore some of these ideas, and give a new characterization of products of projective spaces in terms of the geometry of their families of rational curves of minimal degree.
   
MARCH 27 - 31, 2006
   
PACM Seminar
Topic: Sparsity and Source Separation: just DUET
Presenter: Scott Rickard, Electronic and Electrical Engineering, University College Dublin
Date:  Monday, March 27, 2006, Time: 4:00 p.m., Location: Fine Hall 214
Abstract:

Detroit MI, April 2001.
A woman is found stabbed to death in the kitchen of her apartment. The police find that a video recorder in the family room was recording during the murder, but the camera lens cap was on and, as a result, the video portion of the recording reveals nothing. The audio channel of the recording, however, has captured the entire crime. Unfortunately, a stereo was playing loud schmaltzy music during the conversation leading up to the assault, and the speech on the recording cannot be understood. Fortunately, the police have the tape that was playing at the time, but traditional approaches for removing the interfering music from the mixture fail.
Princeton NJ, June 2002.

Murder victim gets the last word - case closed.

In this talk I will discuss the sparse revolution which is occurring in signal processing which is allowing researchers to solve systems of equations with more unknowns than constraints. We've all been taught that if we have 2 unknowns, we require 2 equations to solve for the unknowns. For 3 unknowns, we need 3 equations (and 4 require 4, and so on...). This is not true - as long as you're willing to cheat. For example, we 'cheat' in cocktail parties when we listen to one person while a dozen speak in the background. Mathematically, we would need 13 ears to eliminate the dozen unwanted speakers to allow us to focus on the one speaker of interest. The DUET Blind Source Separation Algorithm mimics this human auditory ability in that it can separate an arbitrary number of sources from just two mixtures (such as those heard by two ears in a cocktail party). I will reveal how we use sparsity to cheat and thus solve the problem of more unknowns than equations. Also, I will discuss various related modifications of DUET, one of which was used to solve the above murder case. This talk will feature a live demonstration of DUET.

   
Algebraic Geometry Seminar
Topic: Nef but not semi-ample line bundles over finite fields
Presenter: Burt Totaro, Cambridge Univ.
Date:  Tuesday, March 28, 2006, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: We give the first example of a nef line bundle L on a smooth projective variety over a finite field such that L is not semi-ample. (That is, no power of L is basepoint-free.) Our examples give a negative answer to a question by Keel.
   
Topology Seminar *** Please note special date
Topic: Thom polynomials
Presenter: Richard Rimanyi, UNC Chapel Hill
Date:  Tuesday, March 28, 2006, Time: 4:30 p.m., Location: Fine 314
Abstract: In certain situations global topology may force singularities. For example, the topology of the Klein bottle forces self-intersections when mapped into 3-space. Any map of the projective plane must have at least cusp singularities when mapped into the plane. The topology of a manifold may force any differential form on it to degenerate at certian points. In a family of vector bundles over a complex curve some must degenerate to a non-stable bundle (in the GIT sense), depending on the topology of the family. In a family of vector bundle maps---arranged according to a directed graph (quiver)---some may be forced to degenerate. In families of linear spaces some have special incidence with some other fixed ones (Schubert calculus). --- These degenerations are governed by a unified notion in equivariant cohomology, the Thom polynomial of "singularities". In the lecture I will review Thom polynomials, computational strategies (interpolation, localization, Grobner basis), show examples and applications.
   
Discrete Mathematics Seminar
Topic: Making, Breaking, Avoiding, Enforcing
Presenter: Tibor Szabo, ETH
Date:  Wednesday, March 29, 2006, Time: 2:15 p.m., Location: Fine 224
Abstract: See http://www.math.princeton.edu/~bsudakov/szabo2005-2006.pdf
   
Geometry, Representation Theory, and Moduli Seminar
Topic: The B model partition function and the holomorphic anomaly equation
Presenter: K. Costello, University of Chicago
Date:  Wednesday, March 29, 2006, Time: 3:00 p.m., Location: Fine Hall 214
Abstract: If X is a Calabi-Yau, the B model partition function is a state in the Fock space of the symplectic vector space H*(X)((t)). The holmorphic anomaly equation tells us how this behaves when we vary the complex structure on X : the partition function is flat for a certain natural connection on the Fock space. I'll discuss some aspects of the construction of the partition function and the proof of the holomorphic anomaly.
   
Department Colloquium
Topic: TBA
Presenter: Gang Tian, Princeton University
Date:  Wednesday, March 29, 2006, Time: 4:30 p.m., Location: Fine Hall 314
   
Algebraic Topology Seminar
Topic: Homotopy exponents of compact simple Lie groups
Presenter: Don Davis, Lehigh University
Date:  Thursday, March 30, 2006, Time: 3:00 p.m., Location: Fine Hall 401
Abstract: We compare lower bounds for homotopy exponents of compact simple Lie groups obtained from v1-periodic homotopy theory with upper bounds obtained from various fibrations, following ideas of Theriault, often obtaining very good agreement.
   
Topology Seminar
Topic: TBA
Presenter: Elisenda Grigsby, UC Berkeley
Date:  Thursday, March 30, 2006, Time: 4:30 p.m., Location: Fine Hall 314
 
Geometric Analysis Seminar
Topic: TBA
Presenter: Qing Jie, UC Santa Cruz
Date:  Friday, March 31, 2006, Time: 3:00 p.m., Location: Fine Hall 314
 
APRIL 3 - 7, 2006
 
Math Graduate Student Seminar
Topic: TBA
Presenter: Louis-Pierre Arguin, Princeton University
Date:  Tuesday, April 4, 2006, Time: 12:30 p.m., Location: Fine Hall 224
   
Mathematical Physics Seminar
Topic: Hardy inequalities for many particles
Presenter: Ari Laptev, KTH
Date:  Tuesday, April 4, 2006, Time: 4:30 p.m., Location: Jadwin 343
Abstract: We prove some inequalities of Hardy type for many particles. In particular, we show how introducing Aharonov-Bohm magnetic fields could give such inequalities for two-dimensional particles. It turned out that 2D Hardy inequalities hold also for fermions.
   
Operation Research and Financial Engineering Seminar
Topic: Solving nonsmooth optimization problems
Presenter: Adrian Lewis, Cornell University
Date:  Tuesday, April 4, 2006, Time: 4:30 p.m., Location: Room E-219, Engineering Quad
Abstract: Practical optimization problems are often nonsmooth, confounding classical, gradient-based algorithms.  A randomized gradient-sampling technique for minimizing nonsmooth functions is simple to understand and implement, and performs well in practice.  I will outline the idea, sketch some theoretical justification, and illustrate it on a challenge problem from robust system control.  Along the way, I will discuss some broader theoretical issues in nonsmooth optimization.

Joint work with J. Burke and M. Overton
   
Discrete Mathematics Seminar
Topic: TBA
Presenter: Daniel Katz, Princeton University
Date:  Wednesday, April 5, 2006, Time: 2:15 p.m., Location: Fine 224
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: Michael Usher, Princeton University
Date:  Wednesday, April 5, 2006, Time: 3:00 p.m., Location: Fine Hall 214
   
Algebraic Geometry Seminar *** Please note special date
Topic: TBA
Presenter: M. Popa, University of Chicago
Date:  Thursday, April 6, 2006, Time: 4:30 p.m., Location: TBA
 
Topology Seminar
Topic: TBA
Presenter: Mikhail Khovanov, Columbia University
Date:  Thursday, April 6, 2006, Time: 4:30 p.m., Location: Fine Hall 314
 
Geometric Analysis Seminar
Topic: TBA
Presenter: Robert Hardt, Rice University
Date:  Friday, April 7, 2006, Time: 3:00 p.m., Location: Fine Hall 314
 
APRIL 10 - 14, 2006
 
PACM Seminar
Topic: Spirochetes and spermatozoa: Fluid dynamic models of microorganism motility
Presenter: Lisa Fauci, Mathematics, Tulane University
Date:  Monday, April 10, 2006, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: The observed swimming behavior of a motile microorganism is the result of a complex interplay between mechanisms of internal force generation, the passive elastic properties of its structure, and a surrounding viscous fluid. In this talk, we will focus on two very different types of microorganisms: the spirochetes, which are a type of bacteria characterized by an efficient mode of motility that allows them to screw through viscous fluids and mucosal surfaces, and spermatozoa, that undulate as a result of the action of thousands of molecular motors positioned along the flagellum. We will present mathematical and computational models that couple the internal force generating mechanisms of these microorganisms with external fluid mechanics. We will describe our methodology, which includes both the method of regularized Stokeslets and the immersed boundary method. We will discuss recent successes as well as challenges associated with these models.
   
PACM Seminar ***Note special date
Topic: From Maxwell demon to Brownian refrigerator
Presenter: Christian Van den Broeck, Theoretical Physics, Hasselt University, Belgium
Date:  Tuesday, April 11, 2006, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: Maxwell was under the impression that it should be possible to violate the second law of thermodynamics provided one could operate on a molecular scale. This comment was the beginning of a discussion stretching over the whole of the 20th century involving outstanding physicists including Smoluchowski, Onsager, Szilard, Feynman and Landauer. The issue has now become of more than academic interest because of recent developments in nanotechnology and molecular biology. We present a simplification of the Feynman ratchet that can be studied in detail by hard disk molecular dynamics and for which an exact microscopic calculation is possible. We will show how this construction can be used as a Brownian motor but also as a Brownian heat pump and refrigerator.
 
Mathematical Physics Seminar
Topic: Integrable models and operator algebras
Presenter: Detlev Buchholz, University of Goettingen
Date:  Tuesday, April 11, 2006, Time: 4:30 p.m., Location: Jadwin 343
Abstract: Recently, it has been possible to establish rigorously the existence of an abundance of 1+1-dimensional relativistic quantum field theories with factorizing scattering matrices by operator-algebraic means. This novel approach, which is complementary to the advanced methods of constructive quantum field theory, settles some long-standing questions in the context of integrable models (form-factor program) and sheds new light on the problem of constructing quantum field theories. In this talk, a survey is given of the basic ideas, results and perspectives of this approach.
   
Operation Research and Financial Engineering Seminar
Topic: TBA
Presenter: Massimo Marinacci
Date:  Tuesday, April 11, 2006, Time: 4:30 p.m., Location: Room E-219, Engineering Quad
 
Discrete Mathematics Seminar
Topic: TBA
Presenter: Roy Meshulam, Technion and IAS
Date:  Wednesday, April 12, 2006, Time: 2:15 p.m., Location: Fine 224
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: Alina Marian, Yale University
Date:  Wednesday, April 12, 2006, Time: 3:00 p.m., Location: Fine Hall 214
   
Geometric Analysis Seminar
Topic: TBA
Presenter: Hubert Bray, Duke University
Date:  Friday, April 14, 2006, Time: 3:00 p.m., Location: Fine Hall 314
 
APRIL 17 - 21, 2006
 
PACM Seminar
Topic: Turbulence and Large-scale Circulation in the Ocean and Atmosphere
Presenter: Geoff Vallis, Geosciences / Atmospheric & Oceanic Sciences, Princeton University
Date:  Monday, April 17, 2006, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: The large-scale circulation is not only affected but is essentially effected by turbulent flows. This turbulence is not the small-scale turbulence that is (unfortunately) sometimes connoted by the word turbulence, but is turbulence up to the scale of the large-scale flow itself. This is largely two-dimensional, so-called geostrophic turbulence. We will discuss what is known and what is unknown about such flow, the problems of both simulating it and of understanding it, and whether these two are the same.
 
Mathematical Physics Seminar
Topic: TBA
Presenter: Y. Peres, University of California, Berkeley
Date:  Tuesday, April 18, 2006, Time: 4:30 p.m., Location: Jadwin 343
 
Discrete Mathematics Seminar
Topic: TBA
Presenter: Noga Alon, Tel Aviv University and IAS
Date:  Wednesday, April 19, 2006, Time: 2:15 p.m., Location: Fine 224
   
Department Colloquium
Topic: TBA
Presenter: Yuval Peres, University of California, Berkeley
Date:  Wednesday, April 19, 2006, Time: 4:30 p.m., Location: Fine Hall 314
 
Analysis Seminar
Topic: TBA
Presenter: Pierre Germain, Ecole Polytechnique, Palaiseau
Date:  Thursday, April 20, 2006, Time: 4:00 p.m., Location: Fine Hall 322
   
Geometric Analysis Seminar
Topic: TBA
Presenter: Mu-Tao Wang, Columbia University
Date:  Friday, April 21, 2006, Time: 3:00 p.m., Location: Fine Hall 314
 
APRIL 24 - 28, 2006
 
Mathematical Physics Seminar
Topic: TBA
Presenter: P. Hislop, University of Kentucky
Date:  Tuesday, April 25, 2006, Time: 4:30 p.m., Location: Jadwin 343
 
Department Colloquium
Topic: TBA
Presenter: Yair Minsky, Yale University
Date:  Wednesday, April 26, 2006, Time: 4:30 p.m., Location: Fine Hall 314
 
Analysis Seminar
Topic: Optimal transportation and Ricci curvature for metric measure spaces
Presenter: Karl-Theodor Sturm, University of Bonn
Date:  Thursday, April 27, 2006, Time: 4:00 p.m., Location: Fine Hall 322
Abstract: We introduce and analyze generalized Ricci curvature bounds for
metric measure spaces (M,d,m), based on convexity properties of the relative entropy Ent(. | m). For Riemannian manifolds, Curv(M,d,m) \ge K if and only if Ric_M\ge K on M. For the Wiener space, Curv(M,d,m)=1. One of the main results is that these lower curvature bounds are stable under (e.g. measured Gromov-Hausdorff) convergence. Moreover, we introduce a curvature-dimension condition CD(K,N) being more restrictive than the curvature bound Curv(M,d,m)\ge K. For Riemannian manifolds, CD(K,N) is equivalent to Ric_M(\xi,\xi)\ge K\cdot |\xi|^2 and dim}(M)\le N. Condition CD(K,N) implies sharp version of the Brunn-Minkowski inequality, of the Bishop-Gromov volume comparison theorem and of the Bonnet-Myers theorem. Moreover, it allows to construct canonical Dirichlet forms with {Gaussian upper and lower bounds} for the corresponding heat kernels.
   
Topology Seminar
Topic: TBA
Presenter: Andras Stipsicz, Renyi Institute of Mathematics
Date:  Thursday, April 27, 2006, Time: 4:30 p.m., Location: Fine Hall 314
 
Geometric Analysis Seminar
Topic: TBA
Presenter: Christina W. Tonnessen-Friedman, Union College
Date:  Friday, April 28, 2006, Time: 3:00 p.m., Location: Fine Hall 314
 
MAY 1 - 5, 2006
 
Algebraic Geometry Seminar
Topic: TBA
Presenter: M.A. de Cataldo, Stony Brook
Date:  Tuesday, May 2, 2006, Time: 4:30 p.m., Location: Fine Hall 322
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: A. Braverman, Brown University
Date:  Wednesday, May 3, 2006, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: Asymptotics for prime specialization over finite fields
Presenter: Brian Conrad, University of Michigan
Date:  Wednesday, May 3, 2006, Time: 4:30 p.m., Location: Fine Hall 314
   
Geometric Analysis Seminar
Topic: TBA
Presenter: Fernando Marques, Stanford University
Date:  Friday, May 5, 2006, Time: 3:00 p.m., Location: Fine Hall 314