Events - February 2019

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

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

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

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

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

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

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

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

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

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

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

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

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

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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