## University COVID-19 update

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

# Events - February 2019

Thursday, February 28, 2019 — 3:30 PM EST

## Special Seminar - Yi-Shuai Niu

Title: Difference-of-SOS and Difference-of-Convex-SOS Decomposition Techniques for Polynomials

 Speaker: Yi-Shuai Niu Affiliation: SJTU-Paristech & Maths department Shanghai Jiao Tong University Room: MC 5501

Abstract:

We are interested in polynomial decomposition techniques for reformulating any multivariate polynomial into difference-of-sums-of-squares (DSOS) and difference-of-convex-sums-of-squares (DCSOS) polynomials.

Wednesday, February 27, 2019 — 3:30 PM EST

## Graphs and Matroids Seminar- Ahmed Ashraf

Title: Cyclic flat approach to matroid base polytopes

 Speaker: Ahmed Ashraf Affiliation: Western University Room: MC 5501

Abstract: Ardila, Benedetti and Doker realised matroid polytopes as generalized permutohedra, and using the work of Postnikov,

Tuesday, February 26, 2019 — 2:00 PM EST

## Reading Group on Entropy and Counting- John Schanck

Title: Bounding Dedekind numbers with entropy

 Speaker: John Schanck Affiliation: University of Waterloo Room: MC 6486

Abstract: The Dedekind numbers (sequence A000372 in the OEIS)

Tuesday, February 19, 2019 — 2:00 PM EST

## **Rescheduled** Reading Group on Entropy and Counting- Jane Gao

Title: Applications of the entropy method: Counting proper colorings of a regular graph

 Speaker: Jane Gao Affiliation: University of Waterloo Room: MC 6486

Abstract: Following Section 6 of Galvin's notes on Entropy and Counting, we will explore Galvin and Tetali’s tight upper bound

Friday, February 15, 2019 — 1:00 PM EST

## Combinatorial Optimization Reading Group- Sharat Imbrahimpur

Title: Coloring 3-colorable graphs with o(n^1/5) colors

 Speaker: Sharat Ibrahimpur Affiliation: University of Waterloo Room: MC 5479

Abstract: This is the second part of the seminar on recent results obtained by Kawarabayashi and Thorup

Thursday, February 14, 2019 — 1:30 PM EST

## Algebraic Graph Theory Seminar- Christopher van Bommel

Title: Quantum Walks, State Transfer, and Entanglement

 Speaker: Christopher van Bommel Affiliation: University of Waterloo Room: MC 6486

Abstract: Quantum walks are the quantum analogues of classical random walks and can be used to model quantum computations.

Wednesday, February 13, 2019 — 3:30 PM EST

## Graphs and Matroids Seminar- James Davies ** Rescheduled**

Title: Circle graphs are quadratically x-bounded

 Speaker: James Davies Affiliation: University of Waterloo Room: **New Room** MC 5501

Abstract: A circle graph $G$ is an intersection graph of a set of chords on a circle.

Friday, February 8, 2019 — 3:30 PM EST

## Tutte Colloquium - Jane Gao

Title: The rank of random matrices over finite fields

 Speaker: Jane Gao Affiliation: University of Waterloo Room: MC 5501

Abstract:

We determine the rank of a random matrix over a finite field with prescribed numbers of non-zero entries in each row and column. As an application we obtain a formula for the rate of low-density parity check codes.

Friday, February 8, 2019 — 1:00 PM EST

## Combinatorial Optimization Reading Group- Tom Kelly

Title:‘Coloring 3-colorable graphs with o(n^1⁄5) colors’ by Kawarabayashi and Thorup

 Speaker: Tom Kelly Affiliation: University of Waterloo Room: MC 5479

Abstract: Much attention has been devoted to nding polynomial time algorithms for coloring three-
colorable graphs with the fewest possible colors.

Thursday, February 7, 2019 — 1:30 PM EST

## Algebraic Graph Theory Seminar- Caelan Wang

Title: Permutation Problems, Chessboards, and Rook Equivalence

 Speaker: Caelan Wang Affiliation: University of Waterloo Room: MC 6486

Abstract: We discuss the motivation and development of the theory around rook polynomials.

Tuesday, February 5, 2019 — 2:00 PM EST

## Reading Group on Entropy and Counting- Jorn van der Pol

Title: Applications of the entropy method: Brégman's theorem

 Speaker: Jorn van der Pol Affiliation: University of Waterloo Room: MC 6486

Abstract: Following Section 5 of Galvin's notes on Entropy and Counting,

Friday, February 1, 2019 — 3:30 PM EST

## Tutte Colloquium - Gabriel Coutinho

Title: Eigenvalue bounds to the (co)clique and chromatic numbers

 Speaker: Gabriel Coutinho Affiliation: Federal University of Minas Gerais, Brazil Room: MC 5501

Abstract:

This is perhaps one of the oldest topics of interest in spectral graph theory, dating back to the works of Hoffman, Haemers, Delsarte and others, in the 70s.

Friday, February 1, 2019 — 1:00 PM EST

## Combinatorial Optimization Reading Group- Rose McCarty

Title: 2-approximation of chromatic number on graph classes excluding a minor

 Speaker: Rose McCarty Affiliation: University of Waterloo Room: MC 5479

Abstract: In this talk we will see a 2-approximation of the chromatic number of graphs excluding a fixed minor.

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