# Events by month

## August 2021

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### Algebraic Graph Theory Seminar - Harmony Zhan

Monday, August 2, 2021 — 11:30 to 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.

### Tutte Colloquium - Liana Yepremyan

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.

### Algebraic Graph Theory Seminar - Judi McDonald

Monday, August 9, 2021 — 11:30 to 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:

### Optimization: Theory, Algorithms, Applications Lecture Series

Wednesday, August 11, 2021 — 10:00 to 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.

### Optimization: Theory, Algorithms, Applications Lecture Series

Wednesday, August 11, 2021 — 11:00 to 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.

### Algebraic Graph Theory Seminar - Lavanya Selvaganesh

Monday, August 16, 2021 — 11:30 to 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.

### August 2021

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