SEMINARS
Updated: 10-17-2007
   
OCTOBER 2007
   
Geometry, Representation Theory, and Moduli Seminar *** Please note special time
Topic: Perverse coherent sheaves on a blowup surface II
Presenter: H. Nakajima, Institute for Advanced Study and Kyoto University
Date:  Wednesday, October 17, 2007, Time: 2:00 p.m., Location: Fine Hall 214
   
Statistical Mechanics Seminar
Topic: Fluctuations in nonequilibrium: classical and quantum
Presenter: Giovanni Gallavotti, University of Rome
Date:  Wednesday, October 17, 2007, Time: 2:00 p.m., Location: Jadwin 343
Abstract: Entropy creation seems quite well understood in classical systems out of equilibrium. Some aspects of this problem and of its possible quantum mechanical version are discussed here in cases in which identifying entropy creation rate as a mechanical observable might be possible.
   
Department Colloquium
Topic: The sum product phenomena and applications
Presenter: Jean Bourgain, Institute for Advanced Study
Date:  Wednesday, October 17, 2007, Time: 4:30 p.m., Location: Fine Hall 314
   
Math Graduate Student Seminar
Topic: In P, or not in P?
Presenter: Sucharit Sarkar, Princeton University
Date:  Thursday, October 18, 2007, Time: 12:30 p.m., Location: Fine Hall 214
Abstract:

I shall define P, NP, L, SL and all those other fancy complexity classes. I shall show why certain problems are NP-complete and mention that L=SL. No prior knowledge is required, the speaker having none himself. There will be pizza. There might be games.

   
Ergodic Theory and Statistical Mechanics Seminar
Topic: Green-Tao's result on arithmetic progressions in the primes: ergodic part of the proof
Presenter: Ilya Shkredov, I.A.S. / Moscow State University
Date:  Thursday, October 18, 2007, Time: 2:00 p.m., Location: Fine Hall 401
Abstract:

Recent and beautiful theorem of Ben Green and Terence Tao asserts that the primes contain arithmetic progressions of any length. The proof has two parts.
In the first part Green and Tao obtain an extension of well-known Szemeredi's theorem on arithmetic progressions. Their proof of the extension is in spirit of ergodic theory. In the second part, using analytical methods, they reduce a question of existence of progressions in the primes to their extension of Szemeredi's theorem.
In our talk we shall discuss the ergodic part of Green-Tao proof.

   
Discrete Mathematics Seminar
Topic: A nearly linear time algorithm for testing membership in minor closed families of graphs
Presenter: Bruce Reed, McGill
Date:  Thursday, October 18, 2007, Time: 2:15 p.m., Location: Fine Hall 224
Abstract: http://www.math.princeton.edu/%7Esnorin/reed2007-fall.pdf
   
Joint Princeton University/IAS Number Theory Seminar
Topic: Linear Equations in Primes
Presenter: Ben Green, University of Cambridge and IAS
Date:  Thursday, October 18, 2007, Time: 4:30 p.m., Location: Fine Hall 214
   
Differential Geometry and Geometric Analysis Seminar
Topic: The Calabi flow on K\"ahler surfaces
Presenter: Weiyong He, UBC
Date:  Friday, October 19, 2007, Time: 3:00 p.m., Location: Fine Hall 314
Abstract: we discuss the formation of the singularities of the Calabi flow with the assumption of uniform bounded Sobolev constant, in particular on K\"ahler surfaces. On some certain K\"ahler surfaces, we can generalize Tian'c condition to get the Sobolev constant a priori and show there is no bubble formed along the flow. It follows that the convergence of the flow and some new existence result of constant scalar curvature metric on certain K\"ahler class.
   
Columbia-NYU-Princeton Algebraic Geometry Seminar *** Please note special date, time, and location
Topic: Modularity and descent in algebraic dynamics
Presenter: E. Hrushovski, University of Jerusalem
Date:  Friday, October 19, 2007, Time: 3:00 p.m., Location: NYU, Warren Weaver Hall, 109
   
Columbia-NYU-Princeton Algebraic Geometry Seminar *** Please note special date, time, and location
Topic: Isotropy of quadratic forms over function fields of p-adic curves
Presenter: R. Parimala,  Emory University
Date:  Friday, October 19, 2007, Time: 4:15 p.m., Location: NYU, Warren Weaver Hall, 109
   
Columbia-NYU-Princeton Algebraic Geometry Seminar *** Please note special date, time, and location
Topic: Log adjunction: effectiveness and positivity
Presenter: V. Shokurov,  Johns Hopkins University
Date:  Friday, October 19, 2007, Time: 5:30 p.m., Location: NYU, Warren Weaver Hall, 109
   
Analysis Seminar
Topic: Global wellposedness and scattering for the mass critical NLS
Presenter: Xiaoyi Zhang, IAS
Date:  Monday, October 22, 2007, Time: 4:00 p.m., Location: Fine Hall 110
Abstract: We present recent work on wellposedness for the mass critical nonlinear Schrodinger equation at the critical regularity. This is joint work with Rowan Killip and Monica Visan.
   
PACM Colloquium
Topic: Shear-induced Mixing
Presenter: Lai-Sang Young, Courant Institute, New York University
Date:  Monday, October 22, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: I will discuss the phenomenon of shear-induced mixing in driven dynamical systems. The unforced system is assumed to have certain simple underlying structures, such as attracting periodic solutions or equilibria undergoing Hopf bifurcations. Specifics of the defining equations are unimportant. A geometric mechanism for producing chaos - or equivalently promoting mixing - is proposed. In the case of periodic kicks followed by long periods of relaxation, rigorous results establishing the presence of strange attractors with SRB measures are presented. These attractors belong in a class of chaotic systems that can be modeled (roughly) by countable-state Markov chains. From this I deduce information on their statistical properties. In the last part of this talk, I will explore numerically the range of validity of the geometric ideas discussed. Examples including stochastically forced coupled oscillators will be presented.
   
Algebraic Geometry Seminar
Topic: Beyond the Hilbert function: what we know and guess about minimal free resolutions
Presenter: David Eisenbud,  University of California at Berkeley
Date:  Tuesday, October 23, 2007, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: I will describe some of what we know about free resolutions and the geometric information they contain, and then explain some recent conjectures of Boij and S\"oderberg. This is the subject of some of my own recent work, in collaboration with Jerzy Weyman, Gunnar Fl\o ystad, and Frank-Olaf Schreyer.
   
Operations Research and Financial Engineering Seminar
Topic: Asset Selection and Under- Diversification with Financial Constraints and Income: Implications for Household Portfolio Studies
Presenter: Stathis Tompaidis, University of Texas at Austin
Date:  Tuesday, October 23, 2007, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: We offer a rational explanation for the observed under-diversification of household porfolios in a complete market, partial equilibrium setting with an investor with CRRA preferences, whose investment opportunity set includes both a riskless asset and multiple risky assets, and who receives an income stream. We show that when the investor faces a margin requirement based on his current wealth, he shifts his portfolio towards undiversified portfolios with fewer assets that offer higher expected returns. We identify the ration of financial wealth to financial wealth augmented by discounted lifetime labor income as the variable that governs the investor's behavior. We also consider the general equilibrium cross-sectional implications of margin requirements in an overlapping-generations model. Joint with Herve Roche.
   
Statistical Mechanics Seminar
Topic: Exact spectral gap for the Kac model with 3D momentum conserving collisions
Presenter: Eric Carlen, Rutgers University
Date:  Wednesday, October 24, 2007, Time: 2:00 p.m., Location: Jadwin 343
Abstract: The Kac model for molecular collisions and its relation to the Boltzmann equation will be reviewed. New results leading to the determination of the exact spectral gap for this model (which governs the rate of approach to equilibrium) will be presented and some open problems concerning entropy will be discussed. (Joint work with J. Geronimo and M. Loss)
   
Department Colloquium
Topic: Castelnuovo-Mumford regularity and Projections of Algebraic Varieties
Presenter: David Eisenbud, University of California at Berkeley
Date:  Wednesday, October 24, 2007, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: Riemann Surfaces were first studied algebraically by first projecting them into the complex projective plan; later the same idea was applied to surfaces and higher dimensional varieties, projecting them to hypersurfaces. How much damage is done in this process? For example, what can the fibers of a general projection look like? This is pretty easy for smooth curves and surfaces (though there are still open questions), not so easy in the higher-dimensional case. I'll explain some of what's known, including recent work of mine with Roya Beheshti, Joe Harris, and Craig Huneke.
   
Discrete Mathematics Seminar
Topic: Sum-product estimate via expanders
Presenter: Van Vu, Rutgers University and IAS
Date:  Thursday, October 25, 2007, Time: 2:15 p.m., Location: Fine Hall 224
Abstract: http://www.math.princeton.edu/%7Esnorin/vu2007-fall.pdf
   
Topology Seminar
Topic: Random walks on the mapping class group
Presenter: Joseph Maher, Oklahoma State
Date:  Thursday, October 25, 2007, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: We show that a random walk on the mapping class group gives rise to a pseudo-Anosov element with asymptotic probability one, i.e. the probability that the end point of the random walk is pseudo-Anosov at time n tends to 1 as n tends to infinity
   
Analysis Seminar
Topic: TBA
Presenter: Lev Kapitanski, University of Miami
Date:  Monday, October 29, 2007, Time: 4:00 p.m., Location: Fine Hall 110
   
NOVEMBER 2007
   
Joint Princeton University/IAS Number Theory Seminar
Topic: Moments of automorphic L-functions, spectral identities, and subconvexity bounds
Presenter: Paul Garrett, University of Minnesota
Date:  Thursday, November 1, 2007, Time: 4:30 p.m., Location: IAS SH-101
   
PACM Colloquium
Topic: Functional Sparsity
Presenter: John Lafferty, Computer Science, Carnegie Mellon University
Date:  Monday, November 5, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: Substantial progress has recently been made on understanding the behavior of sparse linear models in the high dimensional setting, where the number the variables can greatly exceed the number of samples. This problem has attracted the interest of multiple communities, including applied mathematics, signal processing, statistics, and machine learning. But linear models often rely on unrealistically strong assumptions, made more by convenience than conviction. Can we understand the properties of high dimensional nonlinear functions that enable them to be estimated accurately from sparse data? In this talk we present some progress on this problem, showing that many of the recent results for sparse linear models can be extended to the infinite dimensional setting of nonparametric function estimation. In particular, we present some theory for estimating sparse additive models, together with algorithms that are scalable to high dimensions. We illustrate these ideas with an application to functional sparse coding of natural images. This is joint work with Han Liu, Pradeep Ravikumar, and Larry Wasserman.
   
Analysis Seminar
Topic: TBA
Presenter: David Lannes, Universite Bordeaux 1
Date:  Monday, November 5, 2007, Time: 4:00 p.m., Location: Fine Hall 110
   
Algebraic Geometry Seminar
Topic: TBA
Presenter: Rick Miranda,  Colorado State University
Date:  Tuesday, November 6, 2007, Time: 4:30 p.m., Location: Fine Hall 322
   
Statistical Mechanics Seminar
Topic: The thermodynamic limit of quantum Coulomb systems
Presenter: Mathieu Lewin, Universite de Cergy-Pontoise
Date:  Wednesday, November 7, 2007, Time: 2:00 p.m., Location: Jadwin 343
Abstract: I will present a new approach for proving the existence of the thermodynamic limit for quantum systems composed of electrons and nuclei interacting via the Coulomb potential, as in ordinary matter. In particular, I will provide a very general setting that allows us to study many different quantum systems. This is joint work with Christian Hainzl and Jan Philip Solovej.
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: S. Kovács,Washington University
Date:  Wednesday, November 7, 2007, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: TBA
Presenter: Bálint Virág, University of Toronto
Date:  Wednesday, November 7, 2007, Time: 4:30 p.m., Location: Fine Hall 314
   
Ergodic Theory and Statistical Mechanics Seminar
Topic: Deviation of ergodic averages for billiards in polygons
Presenter: Jayadev Athreya, Princeton University / Yale University
Date:  Thursday, November 8, 2007, Time: 2:00 p.m., Location: Fine Hall 401
Abstract: In joint work with G. Forni, we prove polynomial bounds on the deviation of ergodic averages for the billiard flow in Euclidean polygons with rational angles.
   
Joint Princeton University/IAS Number Theory Seminar
Topic: TBA
Presenter: Dinakar Ramakrishnan, Caltech
Date:  Thursday, November 8, 2007, Time: 4:30 p.m., Location: Fine Hall 214
   
Operations Research and Financial Engineering Seminar
Topic: On the Relations Between Implied and Spot Volatilities
Presenter: Valdo Durrleman, Ecole Polytechnique, Paris
Date:  Thursday, November 8, 2007, Time: 4:30 p.m., Location: E-219, E-Quad
Abstract: In the first part of the talk, we will present a result showing how one can compute the spot volatility dynamics from the implied volatility surface. Then, we will look at an application to foreign exchange options: we take the exchange rates EURUSD, USDJPY, and EURJPY and reconstruct the implied volatility smile of one exchange rate from the other two. In the third part of the talk, we study the convergence of at-the-money implied volatilities to the spot volatility in a general model with a Brownian component and a jump component of finite variation. This result is a consequence of the robustness of the Black-Scholes formula and of the central limit theorem for martingales.
   
Topology Seminar
Topic: When knots don't fiber
Presenter: Dan Silver, South Alabama
Date:  Thursday, November 8, 2007, Time: 4:30 p.m., Location: Fine Hall 314
Abstract: In this joint work with Susan Williams we consider the conjecture: a knot is nonfibered if and only if its infinite cyclic cover has uncountably many finite covers. We prove it for a class of knots that includes all knots of genus 1. We also discuss two equivalent forms of the conjecture, one involving twisted Alexander polynomials, the other a weak form of subgroup separability.
   
Symplectic Geometry Seminar
Topic: TBA
Presenter: Hong Qin, Princeton Plasma Physics Laboratory
Date:  Friday, November 9, 2007, Time: 1:30 p.m., Location: Fine Hall 314
   
Differential Geometry and Geometric Analysis Seminar
Topic: TBA
Presenter: Bill Minicozzi, JHU
Date:  Friday, November 9, 2007, Time: 3:00 p.m., Location: Fine Hall 314
   
Symplectic Geometry Seminar ***Please note special date and time
Topic: TBA
Presenter: Bernd Siebert, Universität Freiburg
Date:  Monday, November 12, 2007, Time: 1:30 p.m., Location: Fine Hall 314
   
PACM Colloquium
Topic: Coherent and convex risk measures: representation results and dynamic consistency conditions
Presenter: Patrick Cheridito, Operations Res & Financial Eng, Princeton University
Date:  Monday, November 12, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: Coherent and convex risk measures were introduced to address drawbacks of traditional risk measures such as variance, value-at-risk or default probability. After a short introduction I will give representation results for static risk measures. Then I will discuss dynamic risk measures and conditions for time-consistency.
   
Algebraic Geometry Seminar
Topic: TBA
Presenter: Sai-Kee Yeung,  Purdue University
Date:  Tuesday, November 13, 2007, Time: 4:30 p.m., Location: Fine Hall 322
   
Symplectic Geometry Seminar ***Please note special, date, location and time
Topic: TBA
Presenter: Bernd Siebert, Universität Freiburg
Date:  Wednesday, November 14, 2007, Time: 1:30 p.m., Location: Fine Hall 801
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: S. Gukov, IAS and Santa Barbara
Date:  Wednesday, November 14, 2007, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: TBA
Presenter: Isaac Held, NOAA and Princeton
Date:  Wednesday, November 14, 2007, Time: 4:30 p.m., Location: Fine Hall 314
   
Discrete Mathematics Seminar *** Please note new date
Topic: TBA
Presenter: Peter Keevash, Caltech
Date:  Thursday, November 15, 2007, Time: 2:15 p.m., Location: Fine Hall 224
   
Symplectic Geometry Seminar
Topic: TBA
Presenter: Bernd Siebert, Universität Freiburg
Date:  Friday, November 16, 2007, Time: 1:30 p.m., Location: Fine Hall 314
   
Differential Geometry and Geometric Analysis Seminar
Topic: TBA
Presenter: Michael Eichmair, Stanford University
Date:  Friday, November 16, 2007, Time: 3:00 p.m., Location: Fine Hall 314
   
PACM Colloquium
Topic: A Hierarchy of Mathematical Models for Studying the Earth's Climate
Presenter: Dargan Frierson, Atmospheric Sciences, University of Washington
Date:  Monday, November 19, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: The Earth's climate is a remarkably complex physical system; constructing models to study it is a difficult task which requires parameterization of a multitude of physical processes. Not surprisingly, such models quickly become difficult to understand due to the vast number of nonlinear processes that are active in them. Therefore, an important line of work in atmospheric science involves the development and use of intelligently chosen idealized models, designed to better understand the results of comprehensive climate models as well as the fundamental dynamics of atmospheric circulations. These models are simpler to interpret than the full climate models, but hopefully can still provide insight into the dynamics of their more complex cousins. In this talk, we give a summary of some topical problems in climate dynamics, and the hierarchical modeling approach we have used to study them. We will discuss physical problems such as the predicted poleward shift of the midlatitude jet stream with global warming, and changes in energy fluxes and temperature gradients in the atmosphere. Focusing on the effect of moist convection on these issues, we present a variety of idealized models that we have used to study these problems. These range from models of 3-D fluid motion on a rotating sphere in the presence of condensation, to highly idealized 1-D PDE models of diffusive energy transport.
   
Algebraic Geometry Seminar
Topic: Congruence for rational points over finite fields and coniveau over local fields
Presenter: Chenyang Xu,  Princeton University
Date:  Tuesday, November 20, 2007, Time: 4:30 p.m., Location: Fine Hall 322
Abstract: http://www.math.princeton.edu/alggeom/public_html/xu.pdf
   
Differential Geometry and Geometric Analysis Seminar
Topic: TBA
Presenter: Simon Brendle, Stanford University
Date:  Friday, November 30, 2007, Time: 3:00 p.m., Location: Fine Hall 314
   
Columbia-NYU-Princeton Algebraic Geometry Seminar *** Please note special date and time
Topic: The Jacobian problem
Presenter: Shreeram Abhyankar, Purdue University
Date:  Friday, November 30, 2007, Time: 3:30 p.m., Location: Fine Hall 322
   
Columbia-NYU-Princeton Algebraic Geometry Seminar *** Please note special date and time
Topic: TBA
Presenter: Christopher Hacon,  University of Utah
Date:  Friday, November 30, 2007, Time: 5:00 p.m., Location: Fine Hall 322
   
DECEMBER 2007
   
PACM Colloquium
Topic: Cartesian Cut Cell Methods: Where Do Things Stand?
Presenter: Marsha Berger, Courant Institute, New York University
Date:  Monday, December 3, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract: We discuss some of the steps involved in preparing for and carrying out a fluid flow simulation in complicated geometry. Our goal is to automate this process as much as possible to enable high quality inviscid flow calculations. We use multilevel Cartesian meshes with irregular cells only in the region intersecting a solid object. We present some of the technical issues involved in this approach, including the special discretizations needed to avoid loss of accuracy and stability at irregular boundary cells, as well as how we obtain highly scalable parallel performance. This method is in routine use for aerodynamic calculations in several organizations, including NASA Ames Research Center. Many open problems are discussed.
   
Algebraic Geometry Seminar
Topic: TBA
Presenter: Nicholas Katz,  Princeton University
Date:  Tuesday, December 4, 2007, Time: 4:30 p.m., Location: Fine Hall 322
   
Geometry, Representation Theory, and Moduli Seminar
Topic: TBA
Presenter: A. Zinger, Stony Brook
Date:  Wednesday, December 5, 2007, Time: 3:00 p.m., Location: Fine Hall 214
   
Department Colloquium
Topic: TBA
Presenter: Clifford Taubes, Harvard University
Date:  Wednesday, December 5, 2007, Time: 4:30 p.m., Location: Fine Hall 314
   
Joint Princeton University/IAS Number Theory Seminar
Topic: TBA
Presenter: Jan Bruinier, University of Cologne
Date:  Thursday, December 6, 2007, Time: 4:30 p.m., Location: Fine Hall 214
   
Symplectic Geometry Seminar
Topic: A Sharp Compactness Theorem for Genus-One Pseudo-Holomorphic Maps and Applications
Presenter: Aleksey Zinger, Stony-Brook University
Date:  Friday, December 7, 2007, Time: 1:30 p.m., Location: Fine Hall 314
Abstract: Moduli spaces of stable maps are often called ``compactifications" of spaces of maps from smooth domains. In general, however, the latter are not dense in former. For the model target space P^n, the moduli space of genus 0 maps is an honest compactification, but positive genus moduli spaces have components of different dimensions. This seemingly technical point leads to very different and generally poorly understood behavior of positive-genus Gromov-Witten invariants. In this talk I will describe a sharp version of Gromov's compactness theorem for genus-one pseudo-holomorphic maps that leads to much smaller ``compactifications" of spaces of maps from smooth domains. These are sharp in my cases, as well as with respect to being naturally. Applications of this compactness theorem include new genus 1 GW-invariants with geometric properties similar to those of genus 0 GW -invariants, better understanding of the standard genus 1 GW-invariants, a natural smooth compactification of the Hilbert scheme of smooth genus 1 curves in P^n, and the proof of the 1993 BCOV mirror symmetry prediction for genus 1 GW-invariants of a quintic threefold.
   
PACM Colloquium
Topic: Collective motion and decision-making in animal groups
Presenter: Iain Couzin, Ecology & Evolutionary Biology, Princeton University
Date:  Monday, December 10, 2007, Time: 4:00 p.m., Location: Fine Hall 214
Abstract:

Animal groups such as bird flocks, insect swarms and fish schools are spectacular, ecologically important and sometimes devastating features of the biology of various species. Outbreaks of the desert locust, for example, can invade approximately one fifth of the Earth's land surface and are estimated to affect the livelihood of one in ten people on the planet. Using a combined theoretical and experimental approach involving insect and vertebrate groups I will address how, and why, individuals move in unison and investigate the principals of information transfer in these groups, particularly focusing on leadership and collective consensus decision-making.

For very large animal groups, despite huge differences in the size and cognitive abilities of group members, recent models from theoretical physics ('self-propelled particle', SPP, models) have suggested that general principles underlie collective motion. Such models demonstrate that some group-level properties may be largely independent of the types of animals involved. I shall present recent experimental work on locusts that validates some of the predictions of simple mechanistic models including a density-dependent "phase transition" from disordered to ordered motion.

Details of the mechanism by which individuals interact, however, also provide important biological insights into swarm behaviour. Using laboratory studies involving nerve manipulation and field experiments we demonstrate that some swarming insects are in effect on a "forced march" driven by cannibalism.

These results will be discussed in the context of the evolution of functional complexity and pattern formation in biological systems.

   
Algebraic Geometry Seminar
Topic: TBA
Presenter: Paul Hacking,  University of Washington
Date:  Tuesday, December 11, 2007, Time: 4:30 p.m., Location: Fine Hall 322