Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 5198884567, ext 33038
PDF files require Adobe Acrobat Reader.
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Title: Type II Matrices
Speaker: Ada Chan Affiliation: York University Room: MC 5479Abstract:
In 1867, Sylvester defined an {\sl inverse orthogonal matrix} as an $n\times n$ complex matrix $W$ satisfying
Title: Discrete diffusion on graphs and real hyperplane arrangements
Speaker: David Wagner Affiliation: University of Waterloo Room: MC 6483Abstract:
In 2016, Duffy et al. introduced the following process on a graph. Initially, each vertex has some integer number of ``chips'' placed there (possibly negative).
Title:
Speaker: Lise Turner Affiliation: University of Waterloo Room: MC 5501Abstract:
There are several different notions of what it means for a graph to converge. One popular notion for sparse graphs is BenjaminiSchramm convergence which focuses on local properties of the graphs.
Title: Greedy Heuristic for Maximizing Submodular Set Functions
Speaker: Ishan Bansal Affiliation: University of Waterloo Room: MC 5417Abstract:
Several hard combinatorial optimization problems can be posed in the following framework: maximize a submodular function over its domain subject to a cardinality constraint.
Title: Extending drawings of K(n) to pseudolines and pseudocircles
Speaker: Bruce Richter Affiliation: University of Waterloo Room: MC 5501Abstract:
In the early part of the 21st century, it was shown that the number of crossings in a straightline drawing of K(n) is at least the number H(n), which is conjectured to be the crossing number of K(n). In fact, it is now known that, for n at least 10, the inequality is strict.
Title: Quantum Colouring and Derangements
Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5479Abstract:
Work in quantum information has lead to the introduction of quantum colourings.
Title: Scattering amplitudes and associahedra
Speaker: Hugh Thomas Affiliation: UQAM Room: MC 5417Abstract:
The classic approach to scattering amplitudes sums a contribution from a (potentially very large) number of Feynman diagrams.
Title: A Pseudoforest Analogue of the Strong Nine Dragon Tree Conjecture
Speaker: Logan Grout Affiliation: University of Waterloo Room: MC 5501Abstract:
In 2016, Jiang and Yang proved the Nine Dragon Tree Conjecture, a strengthening of the classical arboricity result of NashWilliams (1964). On the way to developing this proof, Fan, Lim Song, and Yang proved an analogous result for decomposing graphs into pseudoforests, which is a strengthening of Hakimi’s Theorem.
Title: Maximizing a Monotone Submodular Function subject to a Matroid Constraint
Speaker: Justin Toth Affiliation: University of Waterloo Room: MC 5417Abstract:
Based on the paper by Calinescu, Chekuri, Pál, and Vondrák of the same title. We will study a randomized $(1\frac{1}{e})$approximation algorithm for the titular problem.
Title: On the depth of cutting planesOn the depth of cutting planes
Speaker: Laurent Poirrier Affiliation: University of Waterloo Room: MC 5501Abstract:
We tackle one of the most important open problems in computational integer programming: cut selection.
For four decades, cutting planes were believed to be useful only for structured combinatorial problems. This changed in 1995 when Balas, Ceria and Cornuéjols showed that Gomory cuts could helpfully strengthen the formulation of general integer programming problems. Since then, many other cut generation techniques have been developed, but their practical success has been moderate at best.
Title: Discrete quantum walks, embeddings and designs
Speaker: Harmony Zhan Affiliation: York University Room: MC 5479Abstract:
We construct a quantum walk from an embedding of a graph.
Title: Perfect state transfer on Hadamard diagonalizable graphs
Speaker: Xiaohong Zhang Affiliation: University of Waterloo Room: MC 5479Abstract:
A (weighted) graph whose Laplacian matrix is diagonalizable by a Hadamard matrix is said to be Hadamard diagonalizable.
Title: Boundary measurement and sign variation in real projective space
Speaker: John Machacek Affiliation: York University Room: MC 5417Abstract:
Title: Sublinear separators in intersection graphs of convex shapes
Speaker: Rose McCarty Affiliation: University of Waterloo Room: MC 5501Abstract:
A balanced separator of an nvertex graph is set of vertices whose deletion leaves only components of size at most 2n/3.
Title: Cutting a square into triangles of equal area
Speaker: Hayley Reid Affiliation: University of Waterloo Room: MC 5501Abstract:
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.
Title: Perfect state transfer on Cayley graphs
Speaker: Soffia Arnadottir Affiliation: University of Waterloo Room: MC 5479Abstract:
Perfect state transfer on Cayley graphs
Title: Interpolated versions of the Central Limit Theorem, and crossings of pairpartitions
Speaker: Alexandru Nica Affiliation: University of Waterloo Room: MC 5417Abstract:
Title: Edgemaximal graphs on surfaces
Speaker: James Davies Affiliation: University of Waterloo Room: MC 5501Abstract:
It is straightforward to show that, with the exception of small complete graphs, every edgemaximal planar graph triangulates the plane.
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 5198884567, ext 33038
PDF files require Adobe Acrobat Reader.
The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land granted to the Six Nations that includes six miles on each side of the Grand River. Our active work toward reconciliation takes place across our campuses through research, learning, teaching, and community building, and is coordinated within the Office of Indigenous Relations.