# Events

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## Graphs and Matroids Seminar - Alan Arroyo

**Title:** Geometric drawings of graphs (Part I)

Speaker: | Alan Arroyo |

Affiliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract:**

This is the first of two talks about drawings of graphs that arise from geometry.

Part I: Understanding rectilinear drawings.

## 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.

## 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:

## 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.

## 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.

## Graphs and Matroids Seminar - Kasper Lyngsie

**Title:** The 1,2,3-Conjecture and a related problem for bipartite graphs

Speaker: | Kasper Lyngsie |

Affiliation: | University of Waterloo |

Room: | MC 5479 |

**Abstract:**

## 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.

## 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.

## 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.