Events - August 2021

Monday, August 16, 2021 — 11:30 AM EDT

Algebraic Graph Theory Seminar - Lavanya Selvaganesh

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.

Friday, August 13, 2021 — 3:30 PM EDT

RESCHEDULED: Tutte Colloquium - Ahmad Abdi

 Speaker: Ahmad Abdi Affiliation: London School of Economics Zoom: Please email Emma Watson

Abstract:

Most linear programming solvers use fixed-precision floating points to approximate the rational numbers. Though successful on most real-world instances, solvers sometimes run into serious issues when carrying out sequential floating-point arithmetic, due to compounded error terms. This practical limitation leads to the following theoretical problem:

Wednesday, August 11, 2021 — 11:00 AM EDT

Optimization: Theory, Algorithms, Applications Lecture Series

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

Optimization: Theory, Algorithms, Applications Lecture Series

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

Algebraic Graph Theory Seminar - Judi McDonald

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

Tutte Colloquium - Liana Yepremyan

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

Algebraic Graph Theory Seminar - Harmony Zhan

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.

July 2021

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