# Seminars & Events for 2010-2011

March 23, 2010
12:30pm - 1:30pm
##### The Conquest of Topology by Algebra, or, Topological Spaces as Relational Beta-Modules
###### Graduate Student Seminar

We explore the relationship between topological spaces and modules of the ultrafilter monad, Beta. Several basic properties of topological spaces X are rephrased as properties of "convergence" relations $BX--->X$.

Speaker: Owen Biesel,
Location:
Fine Hall 314
August 25, 2010
2:00pm - 4:00pm
##### Hidden symmetries and decay for fields outside a Kerr black hole
###### Analysis Seminar

The Kerr solutions to Einstein's equations describe rotating black holes. For the wave equation in flat-space and outside the non-rotating, Schwarzschild black holes, one method for proving decay is the vector-field method, which uses the energy-momentum tensor and vector-fields.

Speaker: Pieter Blue, University of Edinburgh
Location:
Fine Hall 314
September 13, 2010
2:00pm - 4:00pm
##### Narcissistic Skyrmions
###### Analysis Seminar

The Skyrme model is a nonlinear sigma-model whose topologically non-trivial target space allows the existence of so-called topological solitons. Such solitons were proposed by Skyrme to model nuclear matter. In this talk I will review the history of the model and present recent work with Gary Gibbons and Willie Wong ruling out the existence of solitons with a planar reflection symmetry.

Speaker: Claude Warnick, University of Cambridge
Location:
Fine Hall 314
September 16, 2010
2:30pm - 4:30pm
##### Unfriendly partition of graphs without an infinite subdivided clique
###### Discrete Mathematics Seminar

In this talk I prove that every graph with less than $\aleph_\omega$ vertices, which does not contain a subdivision of an infinite clique as a subgraph, must have a partition of its vertices to two sets, so that no vertex has more neighbors in its own set than in the other set.

Speaker: Eli Berger, University of Haifa
Location:
Fine Hall 224
September 17, 2010
2:00pm - 4:00pm
##### Dynamics of 2D point vortics and its generalizations
###### Ergodic Theory & Statistical Mechanics
Speaker: Tadashi Tokieda, University of Cambridge
Location:
Fine Hall 401
September 20, 2010
4:00pm - 6:00pm
##### Optimal Error Estimates in Stochastic Homogenization
###### Analysis Seminar

Joint Analysis/PACM Colloquium

Speaker: Felix Otto, Max-Planck Institute of Mathematical Sciences, Leipzig, Germany
Location:
Fine Hall 214
September 22, 2010
4:30pm - 6:30pm
##### Optimal bounds on the Kuramoto-Sivashinsky equation
###### Department Colloquium
Speaker: Felix Otto, Max-Planck Institute of Mathematical Sciences, Leipzig, Germany
Location:
Fine Hall 314
September 23, 2010
2:30pm - 4:30pm
##### Asymptotic extremal graph theory is non-trivial
###### Discrete Mathematics Seminar

Many fundamental theorems in extremal graph theory can be expressed as linear inequalities between homomorphism densities. Lovasz and, in a slightly different formulation, Razborov asked whether it is true that every such inequality follows from a finite number of applications of the Cauchy-Schwarz inequality. In this talk we will show that the answer to this question is negative.

Speaker: Sergey Norin, Princeton University
Location:
Fine Hall 224
September 24, 2010
3:00pm - 5:00pm
##### Gradient Ricci Solitons
###### Differential Geometry & Geometric Analysis Seminar

We present some recent development in the study of gradient shrinking Ricci solitons. We address some questions about their classification and their geometric and topological structure.

Speaker: Ovidiu Munteanu, Columbia University
Location:
Fine Hall 314
September 27, 2010
4:00pm - 6:00pm
##### Still running! Recent work on the neuromechanics of insect locomotion
###### PACM/Applied Mathematics Colloquium

I will describe several models for running insects, from an energy-conserving biped with passively-sprung legs to a muscle-actuated hexapod driven by a neural central pattern generator(CPG). Phase reduction and averaging theory collapses some 300 differential equations that describe this neuromechanical model to 24 one-dimensional oscillators that track motoneuron phases.

Speaker: Philip Holmes, Princeton University
Location:
Fine Hall 214
September 28, 2010
4:30pm - 6:30pm
##### Derived Equivalence and the Picard Variety
###### Algebraic Geometry Seminar

I will explain a result, joint with Mihnea Popa, saying that if two smooth projective varieties have equivalent derived categories of coherent sheaves, then their Picard varieties are isogeneous; in particular the number of independent holomorphic one-forms is a derived invariant. A consequence of this is that derived equivalent threefolds have the same Hodge numbers.

Speaker: Christian Schnell, University of Illinois at Chicago (UIC)
Location:
Fine Hall 322
September 30, 2010
2:00pm - 4:00pm
##### Dynamical stability in the planar surface tension problem for the Gates-Penrose-Lebowitz free energy function and Kawasaki dynamics
###### Statistical Mechanics Seminar

The planar surface tension problem for the Gates-Penrose-Lebowitz free energy function concerns the minimization of this functional for profiles $m(x,y)$ on a cylinder in $R\times C\in R^d$ with cubic cross section $C$ and periodic boundary conditions.

Speaker: Eric Carlen, Rutgers University
Location:
Jadwin Hall 343
September 30, 2010
2:30pm - 4:30pm
##### Bounding chromatic number for graphs in Forb*(bull)
###### Discrete Mathematics Seminar

Given a graph $H, Forb(H)$ is the class of all graphs that do not contain $H$ as an induced subgraph, and $Forb^*(H)$ is the class of all graphs that do not contain any subdivision of $H$ as an induced subgraph.

Speaker: Irena Penev, Columbia University
Location:
Fine Hall 224
October 4, 2010
4:00pm - 6:00pm
##### Vertex-disjoint paths in tournaments
###### PACM/Applied Mathematics Colloquium

The question of linking pairs of terminals by disjoint paths is a standard and well-studied question in graph theory. The setup is: given vertices$s1,\ldots,sk$ and $t1,\ldots,tk$, is there a set of disjoint path $P1,\ldots,Pk$ such that $Pi$ is a path from $si$ to $ti$?

Speaker: Maria Chudnovsky, Columbia University
Location:
Fine Hall 214
October 5, 2010
4:30pm - 6:30pm
##### Gradient ideals
###### Algebraic Geometry Seminar

Zero schemes of exact 1-forms have received more attention recently as moduli spaces associated to Calabi-Yau threefolds; they are called gradient schemes or critical schemes.

Speaker: Yu-Han Liu, Princeton University
Location:
Fine Hall 322
October 6, 2010
2:00pm - 4:00pm
##### Phase transition in kinetically constrained models
###### Statistical Mechanics Seminar

Kinetically constrained models are simple lattice models of glasses with a dynamical frustration: a move can be performed only if some local constraints are satisfied, for example if the local density is low enough. These models have been introduced to explain on a purely dynamical ground the glass forming phenomenology.

Speaker: Thierry Bodineau, Ecole Normale Superieur, Paris
Location:
Jadwin Hall 343
October 6, 2010
4:30pm - 6:30pm
##### Blow-up phenomena for the Yamabe equation
###### Department Colloquium

The Yamabe problem asserts that any Riemannian metric on a compact manifold can be conformally deformed to one of constant scalar curvature. However, this metric is not, in general, unique, and there are examples of manifolds that admit many metrics of constant scalar curvature in a given conformal class.

Speaker: Simon Brendle, Stanford University
Location:
Fine Hall 314
October 7, 2010
2:00pm - 4:00pm
##### Shortest Curves Associated to a Degenerate Jacobi Metric on the two Torus
###### Ergodic Theory & Statistical Mechanics

Let $P$ be a potential on the two torus that takes its minimum value at a unique point m. Set $E_0 := P(m)$. For a real number $E$, let $g_E$ be the Jacobi metric associated to $P$ and $E$. For $E \gt E_0, g_E$ is a Riemannian metric. An ancient theorem of Morse and Hedlund says that a $g_E$-shortest curve in an indivisible homology class is simple.

Speaker: John Mather, Princeton University
Location:
Fine Hall 401
October 7, 2010
2:30pm - 4:30pm
##### Random Graphs and the Parity Quantifier
###### Discrete Mathematics Seminar

The classical zero-one law for first-order logic on random graphs says that for any first-order sentence $F$ in the theory of graphs, the probability that the random graph $G(n, p)$ satisfies $F$ approaches either 0 or 1 as $n$ grows.

Speaker: Swastik Kopparty, IAS
Location:
Fine Hall 224
October 7, 2010
4:30pm - 6:30pm
##### Homology of the curve complex and the Steinberg module of the mapping class group
###### Topology Seminar

The homology of the curve complex is of fundamental importance for the homology of the mapping class group. It was previously known to be an infinitely generated free abelian group, but to date, its structure as a mapping class group module has gone unexplored.

Speaker: Nathan Broaddus, Ohio State University
Location:
Fine Hall 314