# Events

Tuesday, October 31, 2017 — 4:00 PM EDT

## Model Theory Seminar

Rahim Moosa, Department of Pure Mathematics, University of Waterloo

"Isolated types of finite rank"

Tuesday, October 31, 2017 — 2:30 PM EDT

## Computability Learning Seminar

Michael Deveau, Department of Pure Mathematics, University of Waterloo

"Isomorphisms that cannot be coded by computable relations"

When we wish to show that two structures have an isomorphism of a certain degree between them, a standard technique is to carefully choose some computable set $U$ and then show that under a natural isomorphism $f$, the image $f(U)$ has the degree we are interested in. We show a case of two structures isomorphic to $(\omega, <)$ where this method of establishing the degree of the isomorphism between them will not work.

Tuesday, October 31, 2017 — 1:30 PM EDT

## Algebraic Geometry Learning Seminar

Justin Laverdure, Department of Pure Mathematics, University of Waterloo

"Rational maps from reduced schemes"

I'll outline the definition of rational, dominant rational, and birational maps, and use these notions to outline the equivalence of the categories of finitely generated extensions of a field k and that of integral k-varieties. I'll also go over the classical example of rational points on the circle, in the light of rational maps.

MC 5413

Monday, October 30, 2017 — 4:00 PM EDT

## Pure Math Colloquium

Laurent Bienvenu, Montpelier, CNRS

"Randomized algorithms in computability theory"

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

## Analysis Seminar

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.

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

## Geometry & Topology Seminar

Mykola Matviichuk, University of Toronto

"Deformation of Dirac structures via L infinity algebras"

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

## Universal Algebra Seminar

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

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

## Number Theory Seminar

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

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

Leah Duffett, Department of Pure Mathematics, University of Waterloo

"Horned spheres and Schoenflies Theorem"

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

## Branching Processes Learning Seminar

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.

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

## Model Theory Seminar

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

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

## Algebra Seminar

Michael Viscardi, University of California, Berkeley

"Quantum cohomology and 3D mirror symmetry"

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

## Pure Mathematics Colloquium

Damien Roy, University of Ottawa

"Diophantine curiosities"

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

## Analysis Seminar

Yiu-Tung Poon, Iowa State University

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

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

## Geometry and Topology Seminar

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.

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

## Universal Algebra Seminar

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

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

## Analysis Seminar

"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.

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

## Number Theory Seminar

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

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

## Branching Processes Learning Seminar

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"

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

## Model Theory Seminar

Levon Haykazyan, Department of Pure Mathematics, University of Waterloo

"Introduction to Positive Logic"

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

## Algebraic Geometry Learning Seminar

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

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

## Pure Mathematics Colloquium

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

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

## Universal Algebra Seminar

Andrei Krokhin, Durham University

"The complexity of valued constraint satisfaction problems"

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

## Algebra Seminar

Rekha Biswal, Université Laval

"Demazure flags, Chebyshev polynomials and mock theta functions"

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

## Branching Processes Learning Seminar

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'"

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