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Wednesday, October 30, 2019 3:30 pm - 3:30 pm EDT (GMT -04:00)

Joint C&O/PureMath Colloquium - Hayley Reid

Title: Cutting a square into triangles of equal area

Speaker: Hayley Reid
Affiliation: University of Waterloo
Room:  MC 5501

Abstract:

Suppose you are given a square and asked to cut it into n triangles of equal area. If n is even the problem is almost trivial, but when n is odd the problem becomes much harder.

Thursday, October 31, 2019 4:00 pm - 4:00 pm EDT (GMT -04:00)

Graphs and Matroids Seminar - James Davies

Title: Edge-maximal graphs on surfaces

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

Abstract:

It is straightforward to show that, with the exception of small complete graphs, every edge-maximal planar graph triangulates the plane.

Friday, November 1, 2019 1:00 pm - 1:00 pm EDT (GMT -04:00)

Combinatorial Optimization Reading Group - Zishen Qu

Title: Maximizing non-monotone submodular functions

Speaker: Zishen Qu
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

Optimization of non-monotone submodular functions has applications in the maximum cut and maximum directed cut problems for graphs.

Friday, November 1, 2019 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Collouium - Luke Schaeffer

Title: A Quantum Query Complexity Trichotomy for Regular Languages

Speaker: Luke Schaeffer
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

We consider the quantum query complexity of regular languages and discover a surprising trichotomy: each regular language has query complexity either Theta(1), ~Theta(sqrt(n)) or Theta(n). 

Thursday, November 7, 2019 1:00 pm - 1:00 pm EST (GMT -05:00)

Algebraic Graph Theory Seminar - Chris Godsil

Title: Cospectral and strongly cospectral vertices

Speaker: Chris Godsil
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

If $a$ is a vertex in a graph with adjacency matrix $A$, the \textsl{walk module} generated by $a$ is the $A$-invariant subspace spanned by the vectors $A^re_a$, for $r\ge0$.

Thursday, November 7, 2019 3:00 pm - 3:00 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - Kevin Purbhoo

Title: Two-colouring hypersurface complements in open Richardson varities

Speaker: Kevin Purbhoo
Affiliation: University of Waterloo
Room: MC 5417

Abstract: 

Given an algebraic hypersurface $H \subset \mathbb{R}^n$, we can always 2-colour the components of the complement $\mathbb{R}^n \setminus H$ such that adjacent components are of opposite colours.

Thursday, November 7, 2019 4:00 pm - 4:00 pm EST (GMT -05:00)

Graphs and Matroids Seminar - Adam Brown

Title: Counting Pentagons in Triangle-free Binary Matroids

Speaker: Adam Brown
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

Every triangle-free graph with n vertices contains at most (n/5)^5 cycles of length five, and this value is attained by the balanced blowup of the 5-cycle.