# Seminars & Events for Graduate Student Seminar

September 11, 2014
12:30pm - 1:30pm
##### A toy model in fluid dynamics
###### Graduate Student Seminar

Distribution of energy among various Fourier modes and how they fluctuate in a turbulent flow are central questions in fluid dynamics. I will speak about a toy model (introduced by Friedlander Katz Pavlovic) which aims to understand energy transport.

Speaker: In-Jee Jeong, Princeton University
Location:
Fine Hall 314
September 18, 2014
12:30pm - 1:30pm
##### The Gauss Sphere Problem
###### Graduate Student Seminar

The Gauss Sphere Problem is a long-open problem in analytic number theory concerning the number of lattice points in a sphere. In this talk I will discuss a variant of this problem: that of summing a polynomial over the lattice points in a sphere. We will use tools from Fourier analysis, exponential sums and modular forms, to sharpen our estimates step by step.

Speaker: Fan Zheng, Princeton University
Location:
Fine Hall 314
September 25, 2014
12:30pm - 1:30pm
##### On complex geometry of some non-Kahler manifolds
###### Graduate Student Seminar

In the talk we discuss a construction of a large family of complex manifolds. This family includes Hopf and Calabi-Eckmann manifolds. Although the question whether a given differentiable manifold admits a complex structure is extremely hard, our construction completely answers it in the case of manifolds with "large" group of U(1)^m-symmetries. We discuss several very basic geometric characteristics  of these manifolds including Dolbeault cohomology and field of meromorphic functions.

Speaker: Yury Ustinovskiy, Princeton University
Location:
Fine Hall 314
October 2, 2014
12:30pm - 1:30pm
##### Uniform strong primeness in matrix rings
###### Graduate Student Seminar

A ring $R$ is uniformly strongly prime if some finite $S \subseteq R$ is such that for $a,b \in R$, $aSb = \{0\}$ implies $a$ or $b$ is zero, in which case the bound of uniform strong primeness of $R$ is the smallest possible size of such an $S$. The case of matrix rings $R$ is considered. Via vector multiplication and bilinear equations, we obtain alternative definitions of uniform strong primeness, together with new theorems restricting the bound of uniform strong primeness of these rings.

Speaker: Henry Thackeray , Princeton University
Location:
Fine Hall 314
October 9, 2014
12:30pm - 1:30pm
##### Counting n particles in the plane
###### Graduate Student Seminar

How do algebraic geometers "count" the number of ways of putting n points in the plane? I'll explain what Euler characteristic is, what a Hilbert scheme is, and how to compute the Euler characteristic of the Hilbert scheme of n points in the plane. The answer may surprise you, especially if you don't know what those words mean yet. Everything will be defined from scratch.

Speaker: Daniel Litt , Stanford University
Location:
Fine Hall 314
October 16, 2014
12:30pm - 1:30pm
##### Symplectic surfaces vs pseudoholomorphic curves
###### Graduate Student Seminar

Although the first appearence of symplectic manifolds was in physics, they have played a fundamental role in pure math for the last 30 years. A big breakthrough came after the work of Mikhail Gromov, who started the study of pseudoholomorphic curves in symplectic manifolds. This make a connection with ideas coming from algebraic geometry. The same kind of ideas allowed Andreas Floer to introduce Floer's homology which has revolutionized low dimensional topology in the last 20 years. I plan to talk about topological properties of those manifolds and the basic facts about the moduli space of pseudoholomorphic curves in a symplectic manifold and how, once we have constructed it, this gives amazing applications to geometry. I'm also giving a proof of the nonsqueezing theorem of Gromov.

Speaker: Anibal Velozo, Princeton University
Location:
Fine Hall 314
October 23, 2014
12:30pm - 1:30pm
##### Braid Groups and Categorification
###### Graduate Student Seminar

Braid groups are fundamental objects in mathematics and categorification is the process of replacing set-theoretic theorems by category-theoretic analogues. We will connect the two by discussing a categorification of the Temperley-Lieb Algebra which results in a braid group action. We will conclude by discussing how a braid group action leads to a homology theory of links - triply graded link homology recently discovered by Mikhail Khovanov.

Speaker: Amitesh Datta , Princeton University
Location:
Fine Hall 314
November 6, 2014
12:30pm - 1:30pm
##### The p-adic uniformization of some curves
###### Graduate Student Seminar

The classical uniformization theorem classifies Riemann surfaces according to their universal covers, and thus provides an important tool for the study of Riemann surfaces (curves over complex numbers). In the p-adic world, similar results hold for some classes of curves. In this talk, I want to show how Tate did this for some elliptic curves and how Mumford generalized it to curves of higher genus.

Speaker: Pan Lue, Princeton University
Location:
Fine Hall 314
November 13, 2014
12:30pm - 1:30pm
##### Nonabelian Hodge theory and uniformization
###### Graduate Student Seminar

Classical Hodge theory provides a link between the topology and the analytic geometry of a compact Kaehler manifold X via harmonic forms. Similarly, in nonabelian Hodge theory (developed by Simpson based on works of Hitchin, Corlette, Donaldson, Uhlenbeck-Yau, and others), harmonic metrics on vector bundles are used to study the fundamental group of X, a nonabelian topological invariant. In this talk, we give an introduction to these topics. As an application, we sketch a proof of the old uniformization theorem for Riemann surfaces from a Hodge-theoretic point of view.

Speaker: Jun Ho (Peter) Whang , Princeton University
Location:
Fine Hall 314
November 20, 2014
12:30pm - 1:30pm
##### Playing with the waves outside a black hole
###### Graduate Student Seminar

In the recent years, a lot of research has been devoted to the study of the behaviour of scalar waves in the exterior region of black hole spacetimes. This is intimately connected to the problem of non linear stability of such black hole spacetimes as solutions to the Einstein equations. In this talk, we will explore some interesting theorems and results in this area. Of course no physics background is required!

Speaker: Georgios Moschidis, Princeton University
Location:
Fine Hall 314
December 4, 2014
12:30pm - 1:30pm
##### Rationality of Algebraic Varieties
###### Graduate Student Seminar

Finding a rational parametrization for a system of polynomial equations has been studied for a long time, and it leads to the concept of rational varieties. Bézout’s theorem implies that degree 1 and 2 hypersurfaces are rational. It is a hard problem to determine whether a general variety is rational.  For a smooth projective variety to be rational, it is necessary that any (tensor power of) differential form must vanish. This condition is also sufficient for curves and surfaces due to Riemann and Castelnuovo respectively. However, this is not true for higher dimensional varieties by the works of Clemens-Griffiths, Iskovskikh-Manin, Artin-Mumford, Kollár, etc.. In this talk, I will give an introduction to the rationality problem and prove the unirationality of cubic threefolds.

Speaker: Yuchen Liu , Princeton University
Location:
Fine Hall 314
December 9, 2014
11:16am - 11:16am
##### Finding Rational Curves
###### Graduate Student Seminar

Rational curves are one of the most basic objects to look at on an algebraic variety, but they have a large impact on the geometric structure of the variety in which they sit. In this talk we will talk about what are rational curves, why they are useful, and how they are found. In particular we will discuss their role in birational geometry and look at Mori's proof of the bend and break theorem, used to prove certain rational curves exist on an algebraic variety.

Speaker: Charlie Stibitz , Princeton University
Location:
Fine Hall 314
February 5, 2015
12:30pm - 1:30pm
##### Mobius randomness and homogeneous dynamics
###### Graduate Student Seminar

Qualitative approaches to understanding the randomness of the primes offer a first step toward the extremely difficult quantitative challenge of sharply bounding sums involving the Mobius function. Recently, Sarnak has conjectured such a qualitative description that subsumes many previously known examples: any observable sequence of complex numbers from a zero-entropy topological dynamical system must fail to correlate with the Mobius function. I will outline this conjecture, go over some interesting known cases, and describe a bit of my thesis work, in which I aim to prove that the conjecture is true for all zero-entropy dynamics on homogeneous spaces of semisimple Lie groups.

Speaker: Ryan Peckner, Princeton University
Location:
Fine Hall 314
February 12, 2015
12:30pm - 1:30pm
##### Visualizing low-dimensional manifolds
###### Graduate Student Seminar

Knots, 3-manifolds, and 4-manifolds are fundamental objects in topology. I will describe how to represent these objects using knot diagrams, Heegaard diagrams, and Kirby diagrams. We'll see how these pictures are useful for defining and computing invariants.

Speaker: Linh My Truong, Princeton University
Location:
Fine Hall 314
February 19, 2015
12:30pm - 1:30pm
##### An introduction to the 3-D Euler Equations and the breakdown of smooth solutions
###### Graduate Student Seminar

In this talk, I will introduce 3-D Euler equations, basic properties of them including derivations, formulations and related concepts like vorticity. Then I will introduce a classic result about the breakdown of smooth solutions, by Beale-Kato-Majda.

Speaker: Joonhyun La , Princeton University
Location:
Fine Hall 314
February 26, 2015
12:30pm - 1:30pm
##### Geometric Analysis of Wave Equations
###### Graduate Student Seminar

In this talk I will give a basic introduction to wave equations, with particular emphasis on geometric techniques which have proven useful in the study of nonlinear wave equations. Time permitting, I will also discuss some recent results on shock formation and on low-regularity local well-posedness.

Speaker: Ross Granowski , Princeton University
Location:
Fine Hall 314
March 5, 2015
12:30pm - 1:30pm
##### Quantum knot invariants and the volume conjecture
###### Graduate Student Seminar

I'll sketch some of the basics of quantum topology, including how to get knot invariants from a ribbon category and how to construct non-cocommutative Hopf algebras.  Next we'll turn to hyperbolic geometry and discuss how hyperbolic structures on knot complements arise.  Finally, I'll discuss how these two topics are linked via the volume conjecture, and give some directions of current work.

Speaker: Daniel Vitek , Princeton University
Location:
Fine Hall 314
March 12, 2015
12:30pm - 1:30pm
##### Defining varieties over number fields
###### Graduate Student Seminar

Shimura varieties are complex algebraic varieties obtained as quotients of Hermitian symmetric spaces. However, it turns out that they admit canonical models defined over number fields. In this talk I will explain how to define the modular curve X_0(N) over the rationals and introduce the concepts of special points and canonical models for general Shimura varieties.

Speaker: Jun Su , Princeton University
Location:
Fine Hall 314
March 26, 2015
12:30pm - 1:30pm
##### Riemann-Hurwitz
###### Graduate Student Seminar

Using some simple ideas from topology, we'll prove Fermat's Last Theorem and the ABC conjecture, more or less. We'll also describe how to tile your favorite Riemann surfaces with attractive wallpaper.

Speaker: Will Sawin , Princeton University
Location:
Fine Hall 314
April 2, 2015
12:30pm - 1:30pm
##### Tropical Curves and Brill-Noether Theory
###### Graduate Student Seminar

In the past few years, tropical geometry has established itself as an important new field bridging algebraic geometry and combinatorics whose techniques have been used successfully to attack problems in both fields. I'll talk about the basics of tropical geometry, with an emphasis on tropical curves. If time permits, I'll show how tropical geometry can be applied to prove results in Brill-Noether thoery of line bundles on algebraic curves.

Speaker: Akash Sengupta , Princeton University
Location:
Fine Hall 314