## University COVID-19 update

### Questions about buildings and services? Visit the list of Modified Services.

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

# Events by month

## February 2020

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### Graphs and Matroids Seminar - Richard Lang

Thursday, February 6, 2020 — 4:00 PM EST

Title: Minimum degree conditions for Hamilton cycles in hypergrahs

Speaker: Richard Lang Affiliation: University of Waterloo Room: MC 5479

Abstract:

A classic result of Dirac states that a graph in which every vertex is connected to at least half of the other vertices contains a Hamilton cycle. How can we generalize Dirac's theorem to hypergraphs?

### Algebraic Graph Theory Seminar - Chris Godsil

Thursday, February 13, 2020 — 1:00 PM EST

Title: Moore Graphs

Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5417

Abstract:

Moore graphs were introduced by Hoffman and Singleton in a fundamental paper. They can be defined as graphs with diameter $d$ and girth $2d+1$.

### Algebraic Combinatorics Seminar - Brian Chan

Thursday, February 13, 2020 — 2:30 PM EST

Title: A generalization of balanced tableaux and matching problems with unique solutions

Speaker: Brian Chan Affiliation: University of British Columbia Room: MC 5417

Abstract:

In this talk, we consider families of finite sets that we call shellable and that have been characterized by Chang and Hirst and Hughes as being the families of sets that admit unique solutions to Hall's matching problem.

### Graphs and Matroids Seminar - Matt Kroeker

Thursday, February 13, 2020 — 4:00 PM EST

Title: List Colouring and Ohba's Conjecture

Speaker: Matt Kroeker Affiliation: University of Waterloo Room: MC 5479

Abstract:

The question of when the list-chromatic number of a graph G, denoted chi_l(G), equals its chromatic number is fundamental to the theory of list colouring.

### Combinatorial Optimization Reading Group - Kanstantsin Pashkovich

Friday, February 14, 2020 — 1:00 PM EST

Title: The Aggregation Closure is Polyhedral for Packing and Covering Integer Programs

Speaker: Kanstantsin Pashkovich Affiliation: University of Ottawa Room: MC 5417

Abstract:

Recently, Bodur, Del Pia, Dey, Molinaro and Pokutta introduced the concept of aggregation cuts for packing and covering integer programs.

### Algebraic Graph Theory Seminar - Chris Godsil

Thursday, February 20, 2020 — 1:00 PM EST

Title: Triangle-free Strongly Regular Graphs

Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5417

Abstract:

Complete bipartite graphs aside, only five triangle-free strongly regular graphs are known. I will describe some of the background to this topic, with the focus on outlining the construction of the Higman-Sims graph.

### Algebraic Graph Theory Seminar - Sabrina Lato

Thursday, February 27, 2020 — 1:00 PM EST

Title: Linear Programming and Extremal Expanders

Speaker: Sabrina Lato Affiliation: University of Waterloo Room: MC 5417

Abstract:

Nozaki proved a linear programming bound on the number of vertices that depends on the eigenvalues of a graph.

### Algebraic Combinatorics Seminar - Ed Richmond

Thursday, February 27, 2020 — 2:30 PM EST

Title: An equivariant basis for the cohomology of Springer fibers

Speaker: Ed Richmond Affiliation: Oklahoma State University Room: MC 5417

Abstract:

Springer fibers are subvarieties of the flag variety that play an important role in combinatorics and geometric representation theory. In this talk, I will discuss joint work with Martha Precup where we analyze the equivariant cohomology of Springer fibers in type A.

### Graphs and Matroids Seminar - Farbod Yadegarian

Thursday, February 27, 2020 — 4:00 PM EST

Title: Excluding an asymmetric group labelled graph

Speaker: Farbod Yadegarian Affiliation: University of Waterloo Room: MC 5479

Abstract:

There are several models of group labelled graphs. In the simpler, undirected model, for an abelian group Γ, every edge e receives a label γ(e) in Γ.

### Combinatorial Optimization Reading Group - Sean Kafer

Friday, February 28, 2020 — 1:00 PM EST

Title: An Introduction to the Circuits of Polyhedra, The Circuit Diameter, and Their Applications

Speaker: Sean Kafer Affiliation: University of Waterloo Room: MC 5417

Abstract:

The combinatorial diameter of a polyhedron P is the maximum value of a shortest path between two vertices of P, where the path moves along edges of P. Its study is motivated largely by its implications on the running time of the Simplex algorithm.

### Tutte Colloquium - Francisco Rodríguez-Henríquez

Friday, February 28, 2020 — 3:30 PM EST

Title: Parallel strategies for SIDH: towards computing SIDH twice as fast

Speaker: Francisco Rodríguez-Henríquez Affiliation: CINVESTAV-IPN Room: MC 5501

Abstrtact:

Over the last ten years, there has been an intense research effort to find hard mathematical problems that would be presumably hard to solve by a quantum attacker and at the same time could be used to build reasonably efficient public-key cryptoschemes.

### February 2020

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