20142015 Schedule
Date  Title  Speaker 
December 2 @ 5PM  Ghosts of Departed Quantities (abstract)  Mark Hamilton (Mount Allison University) 
October 23 @ 5PM  The Space of Penrose Tilings (abstract)  Jeffrey Im (University of Toronto) 
Giving a Talk
The graduate seminar is held approximately once a month, typically on the first Thursday. The general format is as follows: pizza at 4:30, the talk at 5:00, and we go to the bar afterwards.
If you'd like to give a talk, please email Matt Sourisseau (sourisse [at] math.utoronto.ca) or Jerrod Smith (jerrod.smith [at] utoronto.ca) with your talk title and what day(s) you would prefer. We will then ask you for a short (12 paragraph) abstract the week before the talk so that it can go in the official seminar announcements and posters.
Archive
20132014 Schedule
Date  Title  Speaker 
April 3 @ 6PM 
Ode to a Martingale (abstract)
Not to be confused with certain small birds or equestrian harnesses, a martingale is a concept in probability with interesting applications to PDEs, functional analysis, and mathematical finance. We'll begin by motivating the idea of a martingale as a fair game, and from there give a neat characterization of a zany process called Brownian motion with an intimate connection to the heat equation. We'll then discuss some results concerning martingales in the areas of Hardy spaces and asset pricing.

Matt Sourisseau University of Toronto 
March 27 @ 6PM  A Foray into Knot Theory: The Alexander Polynomial (abstract)
The study of knots in threedimensional space is often done through their projections, called "knot diagrams", onto different planes. A central question then is how to tell, given two such diagrams, whether they represent the same knot. This is typically answered through functions called "knot invariants", the most classical among which is the Alexander polynomial. We will show three different ways of constructing it and mention some of its nice properties. Named after its creator, James Alexander, it first appeared in a paper in 1928 and we will discuss its relevance today, including generalizations to tangles and, timepermitting, categorification.

Iva Halacheva University of Toronto 
March 13 @ 6PM  A Hitchhiker's Guide to Cluster Algebras (abstract)
Cluster algebras are commutative algebras having distinguished "clusters" of generators, with different clusters being related to each other by "mutations". Despite the terminology they are relatively elementary to define (and do not require extensive background), and come equipped with a wealth of nice properties.
Since their definition by Fomin and Zelevinsky (2002), cluster algebras have found numerous applications in geometry, representation theory, physics, and elsewhere. We will provide a brief tour of this theory and some of its many applications. 
Alex Weekes University of Toronto 
March 6 @ 6PM  An Exploration of Ricci Flow (abstract)
Given the recent excitement in mathematical circles over G. Perelman’s solution to the Poincaré Conjecture, you have most likely heard of the terms "Ricci flow". But what exactly is Ricci flow, you may be wondering? The aim of my talk will be to provide an answer to this question. I will briefly cover some of the historical context in which Ricci flow was developed. I then hope to provide an intuitive understanding of what Ricci flow is by discussing a few of its interesting properties and solutions. Lastly, I will comment on some of the resent applications of Ricci flow to current research.

Tracey Balehowsky University of Toronto 
January 30 @ 6PM  Here Be Dragons: An Introduction to the Independence Phenomenon (abstract)  Christopher Eagle University of Toronto 
November 21 @ 5PM  A Tour of Recent Work in Geometric Geometry (abstract)  Parker GlynnAdey University of Toronto 
November 7 @ 5PM  The Mellin Transform in Analytic Number Theory (abstract)  Alexander Dahl University of Toronto 
October 10 @ 5PM  Everything you wanted to know about Snakes & Ladders but were too young to ask (abstract) The traditional children's game, Snakes & Ladders, is currently sold as Chutes
& Ladders by Hasbro. An etailing description of the game advertises: "Chutes and Ladders is ideal for younger children who are still learning to take turns and just beginning to recognize numbers (the spinner stays in the single digits). It's also a gentle introduction to the higher numbers as players climb to 100 at the top of the board. And, thanks to all those chutes and ladders, it's got enough excitement to keep your 7yearold on the edge of her seat." Linear algebra suggests otherwise. Take a chance, hear the talk, but decide for yourself if this "Family Game Night game for preschoolers" really belongs on your holiday shopping list. 
David Muraki Simon Fraser University 
20122013 Schedule
(Not a complete list)
Date  Title  Speaker 
8 November 2012  Airy's rainbow and Stokes' mist: asymptotics through the prism of geometry (abstract)  Brent Pym 
4 October 2012  An application of logic to classical algebra  Chris Eagle 
20102011 Schedule
Date  Title  Speaker 
13 April 2011  Tropicalization and Connection to the Secondary fans  Jessie Yang 
6 April 2011  Kitaev's quantum double model for topological quantum computation  representations, higher categories and extended TQFTs
(abstract)
I will introduce one of the major mathematical models of 'topological quantum computation', the Kitaev's quantum double model. As will be argued by Alexander Kirillov on Thursday, this family of models defined on planar graphs is related to another family, called the LevinWen models. Both families can be viewd as extended 321(0) TQFTs (top dimension is 3 because of 2 spatial + 1 temporal dimensions) arising from the TuraevViro construction on the tensor category labeling the underlying 'stringnets'; alternatively, the same extended TQFTs may also be obtained by applying the ReshetikhinTuraev construction on the tensor category of 'excitations'. Without further ado, I will dive into the Kiteav's description of these models, where the representation theory of quantum doubles (of certain Hopf algebras) plays an important role. A cool thing about these models for topological quantum computation is that (if implemented,) they provide physical realizations of recently invented/popularized mathematical notions of extended TQFTs and higher categories. We can even apply the trendy concept of categorification in this context and produce extended TQFTs for higher dimensional manifolds (e.g. a 43210 theory might describe our spacetime manifold).

Lucy Zhang 
30 March 2011  Exact formulas in random growth and directed polymers
(abstract)
The KardarParisiZhang equation has been widely used in physics as a model of random growth and directed polymers. We will discuss the sense that can be made of the equation, and the nonGaussian fluctuations that describe its universality class.

Jeremy Quastel 
23 March 2011  Variational optimization in economics
(abstract)
In this talk I plan to discuss one of my recent research interests, which involves the application of mathematical techniques from the theory of optimal transportation to one of the central problems in economic theory: Optimal pricing facing informational asymmetry. The monopolist's problem of deciding what types of products to manufacture and how much to charge for each of them, knowing only statistical information about the preferences of an anonymous field of potential buyers, is one of the basic problems analyzed in economic theory. The solution to this problem when the space of products and of buyers can each be parameterized by a single variable (say quality X, and income Y) garnered Mirrlees (1971) and Spence (1974) their Nobel prizes in 1996 and 2001. The multidimensional version of this question is a largely open problem in the calculus of variations (see Basov's book "Multidimensional Screening".) I plan to describe recent work with A Figalli and YH Kim, identifying structural conditions on the value b(X,Y) of product X to buyer Y which reduce this problem to a convex program in a Banach space  leading to uniqueness and stability results for its solution, confirming robustness of certain economic phenomena observed by Armstrong (1996) such as the desirability for the monopolist to raise prices enough to drive a positive fraction of buyers out of the market, and yielding conjectures about the robustness of other phenomena observed Rochet and Chone (1998), such as the clumping together of products marketed into subsets of various dimension. The passage to several dimensions relies on ideas from differential geometry / general relativity, optimal transportation, and nonl
inear PDE.

Rob McCann 
17 March 2011  On Computability of Julia sets
(abstract)
Several years ago Braverman and Yampolsky showed that there exist parameters c such that the polynomial z2+c has a noncomputable Julia set. However, this phenomenon is rare. For allmost all c, J_c is computable set, and we conjecture that it is computable in polynomial time. In my talk I will describe the proof of polytime computability for a large class of parameters c, which is a natural step towards a proof of the conjecture.

Artem Dudko 
9 March 2011  Classical mechanics and symplectic geometry
(abstract)
We will show that Newton's 2nd law F = ma, which is 2nd order in time, can be naturally rewritten as a first order system (Hamilton's equations). This will lead us to define Poisson and symplectic manifolds, and we will see that many basic notions and results from classical mechanical systems can be interpreted geometrically. Armed with geometry, we will then examine some examples in detail, and (time permitting) say a few words about how symplectic geometry can be useful in areas of mathematics outside of classical mechanics.

Jonathan Fisher 
16 February 2011  Basic Financial Derivatives and the BlackScholes PDE
(abstract)
This talk will give an introduction to some simple financial derivatives and the concepts used to price them. We will begin with a description of some basic equity derivatives and perform pricing by noarbitrage arguments in a simple binomial model. We will then consider the continuous case where we derive and solve the BlackScholes PDE using methods of Ito's Calculus. The talk will conclude with descriptions of more complicated equity derivatives and how the BlackScholes PDE must be changed to represent the proper derivative value.

Ryan Donnelly 
2 February 2011  Enrico Bombieri and the Prime Number Theorem
(abstract)
We survey some points of contact between the two topics of the title. The talk is intended for a general mathematical audience.

John Friedlander 
26 January 2011  Twosided chain condition in Leavitt path algebras
(abstract)
Leavitt path algebras are a natural generalization of the Leavitt algebras, which are a class of algebras introduced by Leavitt in 1962. For a directed graph $E$, the Leavitt path algebra $L_K(E)$ of $E$ with coefficients in $K$ has received much recent attention both from algebraists and analysts over the last decade. So far, some of the algebraic properties of Leavitt path algebras have been investigated, including primitivity, simplicity and being Noetherian. First, we explicitly describe the generators of twosided ideals in Leavitt path algebras associated to arbitrary graphs. We show that any twosided ideal $I$ of a Leavitt path algebra associated to an arbitrary graph is generated by elements of the form $(v + \sum_{i=1}^n\lambda_i g^i)(v  \sum_{e\in S} ee^*)$, where $g$ is a cycle based at vertex $v$, and $S$ is a finite subset of $s^{1}(v)$. Then, we use this result to describe the necessary and sufficient conditions on the arbitrary sized graph $E$, such that the Leavitt path algebra associated to $E$ satisfies twosided chain conditions. This is joi nt work with Dr. Gene Abrams, Dr. Jason P. Bell and Dr. Kulumani M. Rangaswamy. 
Pinar Colak 
12 January 2011 13 PM 
TeXFreak  Victor Ivrii 
Date  Title  Speaker 
2 December 2010  Convergence and smoothing properties of Steiner symmetrizations
and other simple rearrangements
(abstract)
Rearrangements were invented in the 19th century as tools for proving the isoperimetric inequality. In the 1970's, rearrangements gained new interest, because they proved useful for less obvious minimization problems in functional analysis. Rearrangements manipulate the shape of a body (or a function) without changing its size (norm), usually by pushing it closer to a centered ball (or a radially decreasing function). For example, Steiner symmetrization introduces a hyperplane of symmetry, Schwarz symmetrization creates an axis of rotation, and polarization moves mass towards the origin across a hyperplane. How well is full radial symmetrization approximated by sequences of such simple rearrangements? How fast do sequences converge, and what smoothing properties do they have? These key questions are subtle, because rearrangements are neither linear, nor spatially localized, and typically do not commmute. In this talk, I will discuss joint work with recent UofT Master's student Marc Fortier on these questions in the context of classical and recent results from the literature. Specifically, I will address conditions for (non)convergence of sequences of Steiner symmetrizations and polarizations, and explain what happens for random sequences. 
Almut Burchard 
25 November 2010  Newton diagrams and applications
(abstract)
One basic result of Calculus 1 can be stated as follows. Suppose the Taylor expansion of a (sufciently smooth) function f(x) near the origin begins as f = x^p + ... + x^(p+1) + ... (with some numerical coeffcients). Then in some new (local) coordinates the function is f = x^p. The moral in higher dimension is: 'for a given power series near the origin only a very few monomials are important'. To formulate the precise criteria one uses the Newton diagram associated to f(x1,...,xn). (This helps to study degenerate minima/maxima, types of saddle points etc.) Today the Newton diagram is an important tool in various areas, e.g. understanding the local embedded geometry/topology of a hypersurface. In particular, if the germ of hypersurface is "generic enough" then the local topology is completely determined by its Newton diagrams. So, various hard topological questions are translated into combinatorial ones. Such hypersurface singularities (nondegenerate with respect to their diagrams) are easy to work with and serve as "baby models". I will give a short introduction to this topic.

Dmitry Kerner 
18 November 2010  A short introduction to curve singularities
(abstract)
Consider a local complex plane analytic curve near the origin. By implicit function theorem a smooth curve can be locally rectiË‰ed, i.e. the curve becomes a line after a local change of coordinates. Singular curves have more local structure. I will speak about the topological and analytic classifations of plane curve singularities. The former is discrete and has simple complete invariants. The latter has moduli. Then I will speak about various invariants (Milnor fibre and its cohomology lattice, links and their embeddings etc.)

Dmitry Kerner 
11 November 2010  Sparse structures in Euclidean space
(abstract)
It is a strange but important fact that there exist "sparse" combinatorial structures which, no matter how they are realized in Euclidean space, must exhibit a significant degrees of "complexity." Constructing such structures relies both on topological techniques (such as the BorsukUlam theorem) and probabilistic techniques (such as the Chernoff bounds). These structures has provided many important counterexamples in geometry, such as counterexamples to the BaumConnes conjecture. In the early '80's, two undergraduates proved that given any arrangement of n points in the plane, there must always exist a point in the plane which lies in at least two ninths of all the induced triangles. This theorem has some important consequences. Recently, it has been shown that there are sparse structures which get arbitrarily close to this bound.

Dominic Dotterrer 
4 November 2010  All started with Weyl
(abstract)
Hermann Weyl was the first who studied seriously asymptotic distribution of eigenvalues (1911) of partial differential operators and formulated what waslater called Weyl's conjecture. In the first part of my talk I will discuss the history of the subject and ideas leading to the proof. This proof was worked out in the framework of Microlocal Analysis which is based on the idea of quantization, and the most useful quantization method was also suggested by H.Weyl (1927): http://en.wikipedia.org/wiki/Weyl_quantization. In the second part of the talk I will discuss quantization, uncertainty principle, quantum and classical dynamics. In the third part of the talk I discuss the proof: main singularity, the role of periodic trajectories in the remainder estimate and their possible contribution to the main part. I will follow the same presentation delivered few years ago: http://weyl.math.toronto.edu:8888/victor2/preprints/Grad_Talk_3.php.

Victor Ivrii 
28 October 2010  Which groups are Lie groups?
(abstract)
In its simplest form, Hilbert's 5th problem asks the following: given a group that is a continuous manifold can we define a differentiable (or even better . analytic) structure on it? Gleason and Montgomery. Zippin in 1940s showed that something much stronger holds: any locally compact topological group "with no small subgroups" is automatically an analytic Lie group. We.ll prove this result in compact case and discuss the general case. Time permitting, we.ll discuss how Gromov used this result to prove his theorem that groups of polynomial growth are virtually nilpotent.

Yevgeniy Likuomovich 
21 October 2010  Covering arrays with row limit four
(abstract)
We are going to introduce covering arrays with row limit (CARLs) and
equivalent families of objects, such as graph coverings and group divisible
covering designs. Also, we are going to present some of the constructions
for CARLs with weight four. This is a talk of ongoing research in
combinatorics, but no previous knowledge of the subject is assumed.

Nevena Francetic 
7 October 2010  Equivalences of the Axiom of Choice
(abstract)
We will look at some of the statements that are equivalent to the axiom of choice, like Zorn's Lemma and the Wellordering Principle. As these statements are used throughout mathematics, every student should see their proofs at least once. We will also look at some "good" and "bad" consequences of the axiom of choice. Finally, we will look at a very bizarre equivalence to the axiom of choice.

Mike Pawliuk 
16 September 2010  The calculus of Euler characteristic and some of its application  Dmitry Kerner 
20092010 Schedule
Date  Title  Speaker 
17 March 2010  The Planar Dimer Model, continued  Alex Bloemendal 
10 March 2010  The Dimer Model on a Planar Domain: From random domino tilings to limit shapes  Alex Bloemendal 
3 March 2010  Renormalization and universality in onedimensional dynamics: critical circle maps  Michael Yampolsky 
17 February 2010  Introduction to the WellPosedness Theory of (Dispersive) PDEs  Hiro Oh 
10 February 2010  Selfreferencing Recursions and Labeled Binary Trees  Abraham Isgur 
3 February 2010  Indecomposable characters on the group S(2∞)  Artem Dudko 
Thursday, 21 January 2010, 2:00 pm  The Calderon problem  from the past to the present  Leo Tzou (Stanford) 
2 December 2009  Asymptoticallyinvariant (AI) sequences in the Heisenberg group  Micheal Pawliuk 
11 November 2009  The Stokes formula, the Cauchy residue theorem, and holomorphic linking  Boris Khesin 
4 November 2009  Rational quaternion algebras and modular forms  Yichao Zhang 
28 October 2009  What is algebra, really?  Omar Antolin Camarena 
21 October 2009  Spiltting random reals  Johanna Franklin 
14 October 2009  Special seminar: Abelian varieties and their moduli spaces  Stephen Kudla 
7 October 2009  Special seminar: Inequalities about lengths, areas, and volumes  Larry Guth 
30 September 2009  Special seminar: Kolmogorov's Solution of Hilbert's 13th Problem  Dror BarNatan 
23 September 2009  Special seminar: Rough Solutions of Nonlinear Schroedinger Equations  James Colliander 
16 September 2009  Special seminar: good bases for representations  Joel Kamnitzer 