# Events

Thursday, September 19, 2019 — 1:00 PM EDT

## Algebraic Graph Theory Seminar - Chris Godsil

TitleOrthogonal Polynomials and the Addition Formula

 Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5479

Abstract:

Many questions about designs and codes in the unit sphere can be reduced to questions about members of a family of orthogonal polynomials, the so-called Gegenbauer polynomials.

Thursday, September 19, 2019 — 3:30 PM EDT

## Algebraic Combinatorics Seminar - Nick Olson-Harris

Title: When are two Schur functions the same?

 Speaker: Nick Olson-Harris Affiliation: University of Waterloo Room: MC 5417

Abstract:

A pair of skew shapes are said to be (skew) equivalent if they admit the same number of semistandard tableaux of any weight; i.e. if their associated skew Schur functions are equal.

Thursday, September 19, 2019 — 4:00 PM EDT

## Graphs and Matroids Seminar - Peter Nelson

Title: The sparsest matroids omitting an independent flat

 Speaker: Peter Nelson Affiliation: University of Waterloo Room: MC 5501

Abstract:

Given integers $k,r \ge 1$, what is the smallest a rank-$r$ matroid can be that does not contain a $k$-element independent set that is also a flat? I will answer this question, characterize the extremal examples, and draw parallels with a problem in graph theory.

Friday, September 20, 2019 — 1:00 PM EDT

## Combinatorial Optimization Reading Group - Chaitanya Swamy

Title: Submodular function maximization

 Speaker: Chaitanya Swamy Affiliation: University of Waterloo Room: MC 5417

Abstract:

I will give the introductory talk for this term's topic for the Combinatorial-Optimization Reading group, namely submodular function maximization. Submodular functions arise in diverse contexts in combinatorial optimization.

Friday, September 20, 2019 — 3:30 PM EDT

## Tutte Colloquium - Douglas Stebila

Title: Undermining key exchange

 Speaker: Douglas Stebila Affiliation: University of Waterloo Room: MC 5501

Abstract:

There are many ways to undermine systems that rely on cryptography. An attacker could of course try to find flaws in the hardware and software implementing the system, or find mathematical weaknesses in the cryptographic algorithms.

Friday, September 27, 2019 — 3:30 PM EDT

## Tutte Distinguished Lecture - Carsten Thomassen

Title: Countable weighted graphs with no unfriendly partitions

### September 2019

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