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Thursday, September 14, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Algebraic Graph Theory Seminar - John Sinkovic

Title: Using eigenvalues to bound the independence number of a graph

Speaker: John  Sinkovic
Affiliation: University of Waterloo
Location: MC 6486

Abstract:

Finding a maximum independent set (or clique) in an arbitrary graph has been shown to be NP-hard.  As any independent set gives a lower bound on the independence number, determining an upper bound is usually more useful. 

Friday, September 15, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Collouium - Chris Godsil

Title: Periodic Vertices in Graphs

Speaker Chris Godsil
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

If $X$ is a graph with adjacency matrix $A$, then any question about the continuous quantum walk on $X$ is a question about the entries of the unitary matrices \[U(t) = \exp(itA)\]

Two pertinent questions are:

Friday, September 22, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Mike Zabrocki

Title: Symmetric group characters as symmetric functions

Speaker: Mike Zabrocki
Affiliation: York University
Room: MC 5501

Abstract:

The irreducible polynomial representations have Schur polynomials as characters. Similarly there is an in-homogeneous basis of symmetric functions that we call the "irreducible character basis" which are characters of irreducible symmetric group modules when the symmetric group is represented as the subgroup of permutation matrices.

Thursday, September 28, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Algebraic Graph Theory Seminar - Christopher van Bommel

Title: Quantum Walks and State Transfer

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. If a quantum walker starts at a vertex of a graph and after some length of time, has probability 1 of being found at a different vertex, we say there is perfect state transfer between the two vertices.

Friday, September 29, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Debbie Leung

Title: The quantum and private capacities of quantum channels, and the solution in the low-noise regime

Speaker: Debbie Leung
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

We first summarize background on the quantum capacity of a quantum channel, and explain why we know very little about this fundamental quantity, even for the qubit depolarizing channel (the quantum analogue of the binary symmetric channel) despite 20 years of effort by the community.

Wednesday, October 4, 2017 4:30 pm - 4:30 pm EDT (GMT -04:00)

Pure Math / Combinatorics and Optimization Joint Colloquium

Title: I'll prove the Fundamental Theorem of Algebra

Speaker: Sam Kim
Affiliation: Department of Pure Math, University of Waterloo
Room: MC 5501

Abstract:

Gauss proved that complex polynomials always admit a root. I'll explain how he came to that conclusion and present a proof that rigorizes his argument in a nice way. You will only need to know a little vector calculus and the intermediate value theorem.

Thursday, October 5, 2017 3:30 pm - 3:30 pm EDT (GMT -04:00)

Graphs and Matroids Seminar - Rong Chen

Title: The 8-connected excluded minors for the class of quasi-graphic matroids

Speaker: Rong Chen
Affiliation: Fuzhou University
Room: MC 5479

Abstract:

The class of quasi-graphic matroids, recently introduced by Geelen, Gerards, and Whittle, is minor closed and contains both lifted-graphic matroids and frame matroids, each of which generalises the class of graphic matroids.