# Events

## October 2017

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### Pure Mathematics Colloquium

Monday, October 2, 2017 — 4:00 PM EDT

**CANCELLED**​

Ragnar-Olaf Buchweitz,  University of Toronto

"The McKay Correspondence Then and Now"

### Algebraic Geometry Learning Seminar

Tuesday, October 3, 2017 — 1:30 PM EDT

Patrick Naylor, Department of Pure Mathematics, University of Waterloo

"The Review Continues"

We'll continue our review from last week. This week, we're actually  defining a scheme, as well as giving a quick review of some of the associated topological properties.

MC 5413

### Model Theory Seminar

Tuesday, October 3, 2017 — 4:00 PM EDT

Peter Sinclair, McMaster University

"Dp-finite fields"

### Branching Processes Learning Seminar

Wednesday, October 4, 2017 — 3:30 PM EDT

Sascha Troscheit, Department of Pure Mathematics, University of Waterloo

"Branching Processes, Martingales, Kingman’s Subadditive Ergodic Theorem, and some applications"

Wednesday, October 4, 2017 — 4:30 PM EDT

Sam Kim, Department of Pure Mathematics, University of Waterloo

"I'll prove the Fundamental Theorem of Algebra"

Gauss proved that complex polynomials always admit a root. I'll explain how he came to that conclusion and present a proof that rigorizes his argument in a nice way. You will only need to know a little vector calculus and the intermediate value theorem. If we have time, I'll show you why a flat triangle has angles that add up to π and why a triangle on a sphere doesn't.

MC 5501

### Number Theory Seminar

Thursday, October 5, 2017 — 1:30 PM EDT
Lucile Devin, University of Ottawa   "Generalizations of Chebyshev's bias"   Following ideas of Rubinstein, Sarnak and Fiorilli, we give a general framework for the study of prime number races and Chebyshev's bias attached to general $L$-functions $L(s) = \sum_{n\geq 1}\lambda_{f}(n)n^{-s}$ satisfying natural analytic hypotheses. We put the emphasis on weakening the required hypotheses such as GRH or linear independence properties of zeros of $L$-functions.

### Universal Algebra Seminar

Thursday, October 5, 2017 — 3:30 PM EDT

Ross Willard, Department of Pure Mathematics, University of Waterloo

"An introduction to finite basis problems"

To get us started this term, I will describe some known instances of the finite basis problem in universal algebra, and one unknown instance that is currently bugging me: “Murskii + L'vov.”  This will be an elementary lecture, intended as a warm-up for Justin’s lectures later this month.

MC 5413

### Geometry and Topology Seminar

Friday, October 6, 2017 — 2:30 PM EDT

Ajneet Dhillon, University of Western Ontario

"Tamagawa numbers and connected components of stacks"

Let X be a smooth projective curve over a finite field and $G$ a semisimple algebraic group over its function field. Let $\mathcal{G}$ be a smooth group scheme over X with generic fiber $G$. The Tamagawa number of $G$ is an arithmetic invariant obtained from a Haar measure on the adelic points of $G$. A conjecture of Harder relates this number to the number of components of the moduli stack of $\mathcal{G}$-bundles.

### Analysis Seminar

Friday, October 6, 2017 — 3:30 PM EDT

Ping Zhong, Department of Pure Mathematics, University of Waterloo

"Estimates for compression norms and additivity violation in quantum information"

### Algebra Seminar

Wednesday, October 11, 2017 — 3:30 PM EDT

Rekha Biswal, Université Laval

"Demazure flags, Chebyshev polynomials and mock theta functions"

### Branching Processes Learning Seminar

Wednesday, October 11, 2017 — 3:30 PM EDT

Sascha Troscheit, Department of Pure Mathematics, University of Waterloo

"Branching Processes, Martingales, Kingman’s Subadditive Ergodic Theorem, and some applications, Part II: The almost sure number of descendants and finer information, such as expected deviations from the average behaviour and `immigration'"

### Universal Algebra Seminar

Thursday, October 12, 2017 — 3:30 PM EDT

Andrei Krokhin, Durham University

"The complexity of valued constraint satisfaction problems"

### Pure Mathematics Colloquium

Monday, October 16, 2017 — 4:00 PM EDT

Karen Yeats, Department of Combinatorics & Optimization, University of Waterloo

"Chord diagram expansions in quantum field theory"

Over the last few years we have been able to re-expand certain series in perturbative quantum field theory using chord diagrams.  These new expansions have nice mathematical structure.  I will give an overview on them and how they can be useful.

MC 5501

### Algebraic Geometry Learning Seminar

Tuesday, October 17, 2017 — 1:30 PM EDT

Diana Castaneda Santos, Department of Pure Mathematics, University of Waterloo

"Review (Episode 3)"

We will continue our review of schemes. We will mention some examples of schemes that are not affine schemes. We will review the proj construction, and more topological properties of schemes. If time permits we'll define morphisms of schemes.

MC 5413

### Model Theory Seminar

Tuesday, October 17, 2017 — 4:00 PM EDT

Levon Haykazyan, Department of Pure Mathematics, University of Waterloo

"Introduction to Positive Logic"

### Branching Processes Learning Seminar

Wednesday, October 18, 2017 — 3:30 PM EDT

Sascha Troscheit, Department of Pure Mathematics, University of Waterloo

"Branching Processes, Martingales, Kingman’s Subadditive Ergodic Theorem, and some applications, Part III: The probability of deviating from the mean behaviour"

### Number Theory Seminar

Thursday, October 19, 2017 — 1:30 PM EDT

John Friedlander, University of Toronto

"Exceptional characters and their consequences"

We review some history about the possible existence of certain Dirichlet characters which might possess a zero very close to the line $Re s = 1$ and the remarkably strong consequences which could be derived under the assumption of their existence.

MC 5501

### Analysis Seminar

Thursday, October 19, 2017 — 2:30 PM EDT

"Cuntz-Nica-Pimsner algebras over $\mathbb{N}^d$"

An effective model for encoding multivariable dynamical systems via C*-algebras is given by Toeplitz-Nica-Pimsner algebras introduced by Fowler. In the work of Carlsen, Larsen, Sims and Vitadello, the right notion of a "boundary quotient" Cuntz-Nica-Pimsner algebra is established, but the precise relations between minimal generators are sometimes very difficult to ascertain.

### Universal Algebra Seminar

Thursday, October 19, 2017 — 3:30 PM EDT

Justin Laverdure, Department of Pure Mathematics, University of Waterloo

"A finite pointed group with no finite basis, Part 1"

We'll go over a construction of Roger Bryant, by building a finite pointed group (P,p) with no finite basis for its laws, as far as we can go. We'll recap basic equational theory stuff, then wade knee-deep into semidirect products and counting arguments.

MC 5413

### Geometry and Topology Seminar

Friday, October 20, 2017 — 2:30 PM EDT

Esther Cabezas-Rivas, Universität Frankfurt

"Ricci flow beyond non-negative curvature conditions"

We generalize most of the known Ricci flow invariant non-negative curvature conditions to less restrictive negative bounds that remain sufficiently controlled for a short time.

### Analysis Seminar

Friday, October 20, 2017 — 3:30 PM EDT

Yiu-Tung Poon, Iowa State University

"(p,q) Matricial Range and Quantum Information Science"

### Pure Mathematics Colloquium

Monday, October 23, 2017 — 4:00 PM EDT

Damien Roy, University of Ottawa

"Diophantine curiosities"

### Algebra Seminar

Tuesday, October 24, 2017 — 11:00 to 11:00 AM EDT

Michael Viscardi, University of California, Berkeley

"Quantum cohomology and 3D mirror symmetry"

### Model Theory Seminar

Tuesday, October 24, 2017 — 4:00 PM EDT

Levon Haykazyan, Department of Pure Mathematics, University of Waterloo

"Introduction to Positive Logic II"

We continue our investigation of positive logic. I will define a new notion of the space of types and I will convince you that it is the right notion.

MC 5403

### Branching Processes Learning Seminar

Wednesday, October 25, 2017 — 3:30 PM EDT

Sascha Troscheit, Department of Pure Mathematics, University of Waterloo

"Branching Processes, Martingales, Kingman’s Subadditive Ergodic Theorem, and some applications, Part IV: Kingman’s Subadditive Ergodic Theorem"

And now for something completely different. We leave Galton-Watson processes behind and talk a bit about Birkhoff’s Ergodic Theorem and Fekete’s Lemma. The latter states that an/n converges if an is a subadditive sequence and Kingman’s subadditive ergodic theorem provides a dynamical / random analogue.

Wednesday, October 25, 2017 — 4:30 PM EDT

Leah Duffett, Department of Pure Mathematics, University of Waterloo

"Horned spheres and Schoenflies Theorem"

### Number Theory Seminar

Thursday, October 26, 2017 — 1:30 PM EDT

Shaoming Guo, Indiana University Bloomington

I will present a few results on counting the numbers of integer solutions of Parsell-Vinogradov systems in higher dimensions. A few techniques from harmonic analysis are crucial in our approach. They are Brascamp-Lieb inequalities, multi-linear Kakeya inequalities, induction on scales, etc.

MC 5501

### Universal Algebra Seminar

Thursday, October 26, 2017 — 3:30 PM EDT

Justin Laverdure, Department of Pure Mathematics, University of Waterloo

"A finite pointed group with no finite basis (part 2)"

We'll continue to go over the construction of Roger Bryant. Hopefully, we'll finally see the group P, and argue that every (n-1)-generated subalgebra of Q_n is in HSP(P).

MC 5413

### Geometry & Topology Seminar

Friday, October 27, 2017 — 2:30 PM EDT

Mykola Matviichuk, University of Toronto

"Deformation of Dirac structures via L infinity algebras"

### Analysis Seminar

Friday, October 27, 2017 — 3:30 PM EDT

Henna Koivusalo, University of Vienna

"Dimensions of sets arising from iterated function systems -- with a special emphasis on self-affine sets"

In this colloquium style talk I will review the history of calculating dimensions of sets that arise as invariant sets of iterated function systems. I will, in particular, compare the theory of self-similar sets to the theory of self-affine sets.

### October 2017

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