# Events - August 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”

### August 2019

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