# Seminars & Events for 2008-2009

September 24, 2008
2:00pm - 4:00pm
##### The effects of quantum protons in hydrogen bonded systems
###### Statistical Mechanics Seminar

Feynman's path integral formulation of equilibrium statistical mechanics allows us to include nuclear quantum effects in computer simulations. This is particularly important when dealing with light particles like the protons participating in hydrogen bonds.

Speaker: Roberto Car, Princeton University
Location:
September 24, 2008
4:30pm - 6:30pm
##### Counting Faces of Randomly-Projected Polytopes, with applications to Compressed Sensing, Error-Correcting Codes, and Statistical Data Mining
###### Department Colloquium
Speaker: David Donoho, Stanford University
Location:
Fine Hall 314
September 25, 2008
12:30pm - 2:30pm
##### Grushko's Theorem
###### Graduate Student Seminar

Grushko's Theorem states that $rank(G*H)=rank(G)+rank(H)$, where $rank$ is the minimum number of generators for a group, and $*$ denotes the free product. We will present Stallings' (topological) proof of Grushko's Theorem.

Speaker: Sucharit Sarkar, Princeton University
Location:
Fine Hall 314
September 25, 2008
2:30pm - 4:30pm
##### An approximate version of Hadwiger's conjecture for claw-free graphs
###### Discrete Mathematics Seminar

Hadwiger's conjecture states that if a graph is not $t$-colorable then it contains the complete graph on $t+1$ vertices as a minor. The case $t=4$ is equivalent to the four color theorem and the case $t=5$ was proved by Robertson, Seymour, and Thomas with the use of the four color theorem. For $t>5$, the conjecture remains open.

Speaker: Alexandra Ovetsky Fradkin, Princeton University
Location:
Fine Hall 224
September 26, 2008
3:00pm - 5:00pm
##### Kähler Ricci flow on Del Pezzo surfaces
###### Differential Geometry & Geometric Analysis Seminar
Speaker: Bing Wang, Princeton University
Location:
Fine Hall 314
September 30, 2008
4:30pm - 6:30pm
##### Pluricanonical maps on threefolds
###### Algebraic Geometry Seminar

We will discuss the problem of effectiveness of Iitaka fibrations for surfaces and threefolds.

Speaker: Gueorgui Todorov, Princeton University
Location:
Fine Hall 322
October 1, 2008
4:30pm - 6:30pm
##### The geometry and topology of arithmetic hyperbolic 3-manifolds
###### Department Colloquium

This talk will discuss recent advances in regards to some of the main open problems about hyperbolic 3-manifolds in the context of arithmetic hyperbolic 3-manifolds.

Speaker: Alan Reid, University of Texas
Location:
Fine Hall 314
October 2, 2008
12:30pm - 2:30pm
##### The Composition Problem in Measure Spaces
###### Graduate Student Seminar

Let $X,Y$ be measurable spaces and $\eta : X \to Y$ be a measurable function. Under what conditions on $\eta$ is the composition with $f : Y \to C$ a well defined operation when $f$ is only specified almost everywhere?

Speaker: Philip J. Isett, Princeton University
Location:
Fine Hall 314
October 2, 2008
4:30pm - 6:30pm
##### Almost minimal laminations and the connectivity of ending lamination space
###### Topology Seminar

We show that if S is a finite type hyperbolic surface which is not the 3 or 4-holed sphere or 1-holed torus, then the Ending lamination space of S is connected, locally path connected and cyclic. Using Klarrich's theorem this implies that the boundary of a curve complex associated to any such space is connected, locally path connected and cyclic.

Speaker: David Gabai, Princeton University
Location:
Fine Hall 314
October 2, 2008
4:30pm - 6:30pm
##### Asymptotics for special derivatives of L-series
###### Princeton University/IAS Number Theory Seminar

In a first part, we shall prove a quantitative nonvanishing result conjectured by Ph.Michel and A.Venkatesh which concerns the special derivatives occuring in the Gross-Zagier formula. Our method relies on two classical equidistribution Theorems in arithmetic geometry. In a second part, we shall explain how to refine these results with methods from analytic number theory.

Speaker: Nicolas Templier, Universite Montpellier II, France and IAS
Location:
IAS Room S-101
October 3, 2008
3:00pm - 5:00pm
##### A new example with positive sectional curvature
###### Differential Geometry & Geometric Analysis Seminar

I will discuss the construction of a new example with positive sectional curvature on a 7-dimensional manifold homeomorphic to the unit tangent bundle of the 4-sphere. The metric is of Kaluza Klein type on an orbifold principle bundle over the 4-sphere and is closely related to the geometry of self dual Einstein and 3- Sasakian metrics.

Speaker: Wolfgang Ziller, University of Pennsylvania
Location:
Fine Hall 314
October 6, 2008
4:00pm - 6:00pm
##### Structure Determination through Eigenvectors of Sparse Operators
###### PACM/Applied Mathematics Colloquium

In many applications, the main goal is to obtain a global low dimensional representation of the data, given some local noisy geometric constraints. In this talk we will show how the problems listed below can be efficiently solved by constructing suitable operators on their data and computing a few eigenvectors of sparse matrices corresponding to the data operators.

Speaker: Amit Singer, Princeton University
Location:
Fine Hall 214
October 6, 2008
4:00pm - 6:00pm
##### A Hyperbolic Free-Boundary Problem for 3D Compressible Euler Flow in Physical Vacuum
###### Analysis Seminar

We prove well-posedness for compressible flow with free-boundary in physical vacuum, modeled by the 3D compressible Euler equations. The vanishing of the density at the vacuum boundary induces degenerate hyperbolic equations that become characteristic, requiring a separate analysis of time, normal, and tangential derivatives to handle the manifest 1/2-derivative loss.

Speaker: Steve Shkoller, University of California, Davis
Location:
Fine Hall 110
October 7, 2008
4:30pm - 6:30pm
##### A Torelli theorem over finite fields
###### Algebraic Geometry Seminar

I will discuss a set-theoretic analog of the classical Torelli theorem for curves.

Speaker: Yuri Tschinkel, New York University
Location:
Fine Hall 322
October 8, 2008
2:00pm - 4:00pm
##### On models of random permutations and their relation to Bose-Einstein condensation
###### Statistical Mechanics Seminar

The first half of the talk will be devoted to probabilistic models of "spatial" random permutations, that involve points in $R^d$. Permutations are weighed according to the length of the jumps. The main question deals with the occurrence of infinite cycles. The second part of the talk will be devoted to the quantum Bose gas in the path-integral representation.

Speaker: Daniel Ueltschi, University of Warwick
Location:
October 9, 2008
12:30pm - 2:30pm
##### Gross—Schoen cycles and triple product L-series
###### Princeton University/IAS Number Theory Seminar
Speaker: Shou-Wu Zhang, Columbia University
Location:
Fine Hall 214
October 9, 2008
12:30pm - 2:30pm
##### GRH and polynomial-time primality testing
###### Graduate Student Seminar

For a long time, a famous open problem was to figure out whether a number was prime quickly (in polynomial time). It's interesting to see how under the generalized riemann hypothesis, the problem becomes completely straightforward. I will introduce the relevant concept and present the simple proof. During the second half, I will present a provably polynomial time test, without reliance on GRH.

Speaker: Jacob Tsimerman, Princeton University
Location:
Fine Hall 314
October 10, 2008
3:00pm - 5:00pm
##### The volume of a differentiable stack
###### Differential Geometry & Geometric Analysis Seminar

We extend to the setting of Lie groupoids the notion of the cardinality of a finite groupoid (a rational number, equal to the Euler characteristic of the correspondingdiscrete orbifold). Since this quantity is an invariant under equivalence of groupoids, we call it the volume of the associatedstack rather than of the groupoid itself.

Speaker: Alan Weinstein, University of California, Berkeley
Location:
Fine Hall 314
October 13, 2008
4:00pm - 6:00pm
##### Simulations of 5-D Plasma Turbulence in Fusion Energy Devices
###### PACM/Applied Mathematics Colloquium

This talk will start with a brief status report on magnetic fusion energy research. One of the key challenges in fusion has been the occurrence of fine-scale turbulent fluctuations, which cause plasma to leak out of a magnetic trap, so we would like to be able to predict and reduce this turbulence.

Speaker: Greg Hammett, Princeton Plasma Physics Lab
Location:
Fine Hall 214
October 13, 2008
4:00pm - 6:00pm
##### Multi-parameter Carnot-Carathéadory balls
###### Analysis Seminar

We discuss multi-parameter Carnot-Carathéadory balls. In particular, we discuss questions motivated by multi-parameter singular integrals. These results generalize results due to Nagel, Stein, and Wainger in the single parameter setting.

Speaker: Brian Street, University of Toronto
Location:
Fine Hall 110