Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 519-888-4567, ext 33038
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Monday, August 16, 2021 11:30 AM EDT
Title: Spectral Properties of the eccentricity matrix for special classes of graphs
| Speaker: | Lavanya Selvaganesh |
| Affiliation: | Indian Institute of Technology (BHU) Varanasi |
| Zoom | Contact Soffia Arnadottir |
Abstract:
Eccentricity matrix, another graph matrix, was originally proposed, as $D_{MAX}$ matrix, by Randi\'c in 2013 and redefined by Wang et al. in 2018 by using the concept of the eccentricities of vertices.
Wednesday, August 11, 2021 11:00 AM EDT
Title: HiGHS: Theory, software and Impact
| Speaker: | Julian Hall |
| Affiliation: | University of Edinburgh |
| Zoom: | Register through The Fields Institute |
Abstract:
Since Dantzig formulated the simplex algorithm in 1947, the widespread need to solve linear optimization problems drove the development of algorithmic and computational techniques for decades, yielding several high performance commercial and open source software systems. This talk will focus on the Edinburgh-based work on solving large scale sparse linear programming problems that underpins the high performance open source linear optimization software, HiGHS, the challenges of developing such software, and the Impact that it has achieved.
Wednesday, August 11, 2021 10:00 AM EDT
Title: TBA
| Speaker: | Jacek Gondzio |
| Affiliation: | University of Edinburgh |
| Zoom: | Register through The Fields Institute |
Abstract:
Having briefly introduced the key ideas which make interior point methods (IPMs) such a powerful optimization approach, I shall focus on a solution of the Newton systems and in particular on the use of iterative (Krylov-subspace) techniques to perform this task.
The Newton systems arising in IPMs are inherently ill-conditioned and preconditioning is a must to make iterative methods work.
A re-design of IPMs to enable the use of iterative techniques provides a completely new perspective on these methods.
I will address both theoretical and practical aspects of it.
Monday, August 9, 2021 11:30 AM EDT
Title: Skew Adjacency Matrices: The Number of Characteristic polynomials of Skew Cacti
| Speaker: | Judi McDonald |
| Affiliation: | Washington State University |
| Zoom: | Contact Soffia Arnadottir |
Abstract:
Friday, August 6, 2021 3:30 PM EDT
Title: The size Ramsey numbers of graphs and hypergraphs
| Speaker: | Liana Yepremyan |
| Affiliation: | London School of Economics |
| Zoom: | Please email Emma Watson |
Abstract:
The s-colour size-Ramsey number of a graph ( hypergraph) H is the minimum number of edges in a graph (hypergraph) G whose every s-edge-colouring contains a monochromatic copy of H. While the study of size Ramsey numbers for graphs goes back to 70's to the work of Erdos, Faudree, Rousseau and Schelp, the systematic study of these numbers for hypergraphs have been initiated much more recently in 2017 by Dudek, La Fleur, Mubayi, and Rödl. In this talk we will present the current known results in the literature, and some recent progress we have made on several questions in the area.
Monday, August 2, 2021 11:30 AM EDT
Title: The average search probability in a quantum walk with an oracle
| Speaker: | Harmony Zhan |
| Affiliation: | York University |
| Zoom: | Contact Soffia Arnadottir |
Abstract:
Some quantum search algorithms can be viewed as discrete-time quantum walks on graphs with a marked vertex a. In such a walk, the oracle is part of the transition matrix, the target state is the characteristic vector of the outgoing arcs of a, and the initial state is the all-ones vector.