# Events - 2019

Thursday, August 15, 2019 — 10:00 AM EDT

## Computability Learning Seminar

Michael Deveau, Department of Pure Mathematics, University of Waterloo

"Computability of Walker's Cancellation Theorem"

Monday, August 12, 2019 — 1:00 PM EDT

## Valuative Tree Seminar

Ehsaan Hossain, Department of Pure Mathematics, University of Waterloo

"Fixed point theorem for trees"

Brett and Matt talked about $V_0$ and $V_\infty$, two different subtrees of the Berkovich plane. All of these are rooted trees. I will either talk about potential theory on trees, or the theorem that every tree map admits a fixed point.

MC 5403

Thursday, August 8, 2019 — 10:00 AM EDT

## Computability Learning Seminar

Luke MacLean, Department of Pure Mathematics, University of Waterloo

"Effectively defining formulas in Robinson's Arithmetic"

It was proven by Alfred Tarski that all general recursive functions are definable in Robinson's Arithmetic. I will give his proof of this fact with supplementary information on how to make the process of finding the defining formula effective.

MC 5479

Tuesday, August 6, 2019 — 2:30 PM EDT

## Algebra Seminar

Abdullahi Umar, Khalifa University of Science and Technology, Abu Dhabi, UAE

''Some Remarks on Monoids of Contraction Mappings of a Finite Chain"

Tuesday, August 6, 2019 — 9:30 AM EDT

## Geometry Working Seminar

Speaker 1: Spencer Whitehead, Department of Pure Mathematics, University of Waterloo

"Regular polytopes and uniform polytopes"

Friday, August 2, 2019 — 10:30 AM EDT

## PhD Thesis Defense

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

"Rational approximations on smooth rational surfaces"

Thursday, August 1, 2019 — 3:30 PM EDT

## Number Theory Seminar

“Apollonian packings and Enriques surfaces”

Tuesday, July 30, 2019 — 1:00 PM EDT

## Valuative Trees Learning Seminar

Matthew Satriano, Department of Pure Mathematics, University of Waterloo

“The valuative tree in action”

A sketch of Xie’s proof of Medvedev-Scanlon for Affine 2-space

Tuesday, July 30, 2019 — 9:00 AM EDT

## Geometry Working Seminar

Anton Iliashenko and Spiro Kargiannis, Department of Pure Mathematics University of Waterloo

“First and Second variation of the Volume functional”

Abstract

In this talk we will derive the first and second variational formulas for the volume functional of a submanifold.

“Vector cross products and calibrations: some non-standard inner product space theory”

Monday, July 29, 2019 — 4:00 PM EDT

## Model Theory Seminar

Martin Hils, Universitat Munster

“Equivariant definable deformation retractions in non-archimedean geometry” (joint work with Ehud Hrushovski and Pierre Simon)”

Monday, July 29, 2019 — 1:30 PM EDT

## Masters Thesis Presentation

Pawel Sarkowicz, Department of Pure Mathematics, University of Waterloo

“Separable Exact C*-Algebras”

Friday, July 26, 2019 — 1:30 PM EDT

Hongdi Huang, Department of Pure Mathematics, University of Waterloo

"The Zariski Cancellation Problem"

Wednesday, July 24, 2019 — 4:30 PM EDT

## Pure Math and C&O Joint Colloquium

Soffia Arnadottir, C&O Department, University of Waterloo

"Graphs in algebra and algebra in graphs"

Tuesday, July 23, 2019 — 2:30 PM EDT

## Geometry & Topology Seminar

Ali Aleyasin, Department of Pure Mathematics, University of Waterloo

"Riemannian cones in disguise: singular elliptic PDEs"

Monday, July 22, 2019 — 1:00 PM EDT

## Valuative Trees Learning Seminar

Brett Nasserden, Department of Pure Mathematics, University of Waterloo

"The valuative tree in action"

Friday, July 12, 2019 — 2:30 PM EDT

## Learning Seminar on Representation Theory of Finite and Infinite Symmetric Groups

Jacob Campbell, Department of Pure Mathematics, University of Waterloo

This is the first meeting of a learning seminar which will run for most of July and August. The proposed day/time for the seminar is on Fridays, 2:30 to 3:30 pm.

In the first few meetings of the seminar we will look at the representation theory of the finite symmetric groups S_n, following the approach of Okounkov and Vershik, which emphasizes the branching rule and the use of Jucys-Murphy elements (all these terms are to be explained as the seminar goes on).

Thursday, July 4, 2019 — 4:00 PM EDT

## Analysis Seminar

Ian Charlesworth, University of California, Berkeley

"Free Stein Irregularity"

Thursday, July 4, 2019 — 10:00 AM EDT

## Computability Learning Seminar

Luke MacLean, Department of Pure Mathematics, University of Waterloo

"Different extensions of first-order logic (part 2)"

Having given definitions and examples of two different extensions of first-order logic, I will proceed to sketch a proof that a computably axiomatizable theory is finitely axiomatizable using additional predicates. Knowledge of the first part is not necessary.

MC 5479

Wednesday, July 3, 2019 — 10:00 AM EDT

## PhD Thesis Defence

Anton Mosunov, Department of Pure Mathematics, University of Waterloo

"Generalizations of the Gap Principle and the Thue-Siegel Principle, With Applications to Diophantine Equations"

Friday, June 28, 2019 — 2:30 PM EDT

## Geometry & Topology Seminar

Sergey Grigorian, University of Texas -- Rio Grande Valley

"Heat Flow of Isometric G2-structures"

Thursday, June 27, 2019 — 10:00 AM EDT

## Computability Learning Seminar

Luke MacLean, Department of Pure Mathematics, University of Waterloo

"Different extensions of first-order logic"

How does one capture the properties that aren’t definable by first-order sentences or even theories? One way is to allow infinitary conjunctions of first-order sentences. Another is to expand the language that is being used. In this talk I will discuss the cases when these two extensions coincide, and sketch a proof by W. Craig and R.L. Vaught that a computably axiomatizable theory can be finitely axiomatized using additional predicates.

Wednesday, June 26, 2019 — 4:00 PM EDT

Carlos Valero, Department of Pure Mathematics, University of Waterloo

"Why we Caré about the Poincaré Conjecture?"

Monday, June 24, 2019 — 2:30 PM EDT

## Analysis Seminar

Roger Smith, Texas A&M University

"A Galois correspondence for crossed products"

We consider a discrete group G acting by outer automorphisms on a simple unital C*-algebra A. We address the problem of characterising the C*-algebras lying between A and its crossed product by G. The main result is that these are parameterised by the subgroups of G. This is joint work with Jan Cameron.

MC 5417

Thursday, June 20, 2019 — 4:00 PM EDT

Eric Boulter, Department of Pure Mathematics, University of Waterloo

"The Parallel Postulate: a 2000-year controversy"

Thursday, June 20, 2019 — 10:00 AM EDT

## Computability Learning Seminar

Mohammad Mahmoud, Department of Pure Mathematics, University of Waterloo

"The Isomorphism Problem of the Class of Computable Trees of Finite Rank"

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