## Contact Info

Pure MathematicsUniversity of Waterloo

200 University Avenue West

Waterloo, Ontario, Canada

N2L 3G1

Departmental office: MC 5304

Phone: 519 888 4567 x33484

Fax: 519 725 0160

Email: puremath@uwaterloo.ca

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

**Michael Deveau, Department of Pure Mathematics, University of Waterloo**

"Computability of Walker's Cancellation Theorem"

Monday, August 12, 2019 — 1:00 PM EDT

**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

**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

**Please note date change**

**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

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

"Regular polytopes and uniform polytopes"

Friday, August 2, 2019 — 10:30 AM EDT

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

"Rational approximations on smooth rational surfaces"

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

**Arthur Baragar, University of Nevada **

“Apollonian packings and Enriques surfaces”

University of Waterloo

200 University Avenue West

Waterloo, Ontario, Canada

N2L 3G1

Departmental office: MC 5304

Phone: 519 888 4567 x33484

Fax: 519 725 0160

Email: puremath@uwaterloo.ca

University of Waterloo

University of Waterloo

43.471468

-80.544205

200 University Avenue West

Waterloo,
ON,
Canada
N2L 3G1