Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 519-888-4567, ext 33038
PDF files require Adobe Acrobat Reader.
Title: Neumaier graphs
Speaker: | Maarten De Boeck |
Affiliation: | University of Memphis |
Location: | Please contact Sabrina Lato for Zoom link |
Abstract: A Neumaier graph is an edge-regular graph with a regular clique. Several families of strongly regular graphs (but not all of them) are indeed Neumaier, but in 1981 it was asked whether there are Neumaier graphs that are not strongly regular. This question was only solved a few years ago by Greaves and Koolen, so now we know there are so-called strictly Neumaier graphs.
Title: Diagrammatic boundary calculus for Wilson loop diagrams
Speaker: | Karen Yeats |
Affiliation: | University of Waterloo |
Location: | MC 6029 |
There will be a pre-seminar presenting relevant background at the beginning graduate level starting at 1pm.
Abstract: This talk is about a different part of the quantum field theory story than I usually talk about. Wilson loop diagrams can be used to index amplitudes in a theory known as N=4 SYM. Suitably nice Wilson loop diagrams are also associated to positroids. For both mathematical and physical reasons it would be nice to have a diagrammatic understanding of the boundaries of the positroid cells of all co-dimensions. While we do not yet have a full understanding, we can build many boundaries with certain diagrammatic moves.
Joint work with Susama Agarwala and Colleen Delaney.
Title: A closure lemma for tough graphs and Hamiltonian ideals
Speaker: | Chinh T. Hoang |
Affiliation: | Wilfrid Laurier University |
Location: | MC 5417 |
Abstract: The closure of a graph $G$ is the graph $G^*$ obtained from $G$ by repeatedly adding edges between pairs of non-adjacent vertices whose degree sum is at least $n$, where $n$ is the number of vertices of $G$. The well-known Closure Lemma proved by Bondy and Chv\'atal states that a graph $G$ is Hamiltonian if and only if its closure $G^*$ is. This lemma can be used to prove several classical results in Hamiltonian graph theory. We prove a version of the Closure Lemma for tough graphs.
Title: Kissing Polytopes
Speaker: | Antoine Deza |
Affiliation: | McMaster University |
Location: | MC 5501 |
Abstract: We investigate the following question: how close can two disjoint lattice polytopes contained in a fixed hypercube be? This question stems from various contexts where the minimal distance between such polytopes appears in complexity bounds of optimization algorithms.
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 519-888-4567, 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 co-ordinated within our Office of Indigenous Relations.