## University COVID-19 update

### Questions about buildings and services? Visit the list of Modified Services.

Please note: The University of Waterloo is closed for all events until further notice.

# Events by date

## Thursday, August 6, 2020

### Algebraic Combinatorics Seminar - Jordan Long

Thursday, August 6, 2020 — 2:30 PM EDT

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.

### Algebraic Combinatorics Seminar - Mushegh Shahinyan

Thursday, August 6, 2020 — 2:30 PM EDT

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.

### Algebraic Combinatorics Seminar - Olha Silina

Thursday, August 6, 2020 — 2:30 PM EDT

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.

### July 2020

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