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# Welcome to Combinatorics and Optimization

Spring 2020 Undergraduate Research Assistantship Program (URA). ***ON-LINE APPICATIONS OPEN November 1, 2019.***

Tutte's Distinguished Lecture Series

The very successful Tutte's 100th Distinguished Lecture Series has now completed. That success has led to a Tutte Distinguished Lecture once per term. The next lecture will happen in the Spring term.

*Recordings of occurred talks are all available on C&O's YouTube Channel

Grad Studies: Fall 2020 applications now open

1. July 17, 2020SAGT 2020 Best Paper Award

Jochen Koenemann, Kanstantsin Pashkovich and Natig Tofigzade were announced the recipients of the SAGT 2020 Best Paper Award for their paper "Approximating Stable Matchings with Ties of Bounded Size".

2. July 1, 2020C&O welcomes four new faculty members

The C&O department is very pleased to welcome four new faculty members, Assistant Professors Logan Crew, Stephen Melczer, Oliver Pechenik and Sophie Spirkl.

3. June 30, 2020Jun Yan awarded an Alumni Gold Medal

At the Spring convocation, Jun Yan was awarded an Alumni Gold Medal in recognition of his academic excellence during his undergraduate studies in Combinatorics & Optimization and Pure Mathematics. Jun Yan was also a recipient of the 2020 William Tutte Centenary Scholarship.

1. Aug. 6, 2020Algebraic Combinatorics Seminar - Jordan Long

Title: Subdivergence-free gluings of trees

 Speaker: Jordan Long Affiliation: University of Waterloo Zoom: Contact Karen Yeats

Abstract:

Motivated by questions in quantum field theory, we introduce a purely combinatorial problem of counting subdivergence-free gluings of trees. We present closed-form expressions counting subdivergence-free gluings for four different families of trees, as well as an algorithm to count subdivergence-free gluings of arbitrary pairs of trees. This is joint work with Clair Dai and Karen Yeats.

2. Aug. 6, 2020Algebraic Combinatorics Seminar - Mushegh Shahinyan

Title: Counting the $c_2$ invariant on the circulant family of graphs

 Speaker: Mushegh Shahinyan Affiliation: University of Waterloo Zoom: Contact Karen Yeats

Abstract:

The algebro-geometric invariant on Feynman Diagrams called the $c_2$ invariant is a useful tool for detecting properties of Feynman periods. We present this identity on graphs that originate from the scalar $\phi_4$-theory with a purely combinatorial perspective and go over some strategies for computing it. We will further narrow our focus onto the circulant family of graphs and present some explicit results.

3. Aug. 6, 2020Algebraic Combinatorics Seminar - Olha Silina

Title: Abelian covering graphs and their properties

 Speaker: Olha Silina Affiliation: University of Waterloo Zoom: Contact Karen Yeats

Abstract:

A covering graph is a structure obtained from a graph by ‘replacing’ every vertex with a coclique of size $r$. The main focus of this talk is connections between (spectral) characteristic of a cover and properties such as being walk- or distance- regular.

All upcoming events