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: Decomposing discrete quantum walks into continuous quantum walks
Speaker: Harmony Zhan Affiliation: York University Zoom: Contact Soffia ArnadottirAbstract:
The Grover walk is a discrete quantum walk inspired by Grover's search algorithm. It takes place on the arcs of a graph, and alternates between "coin flips" and "arc reversal". In this talk, I show that for a distance regular graph X with diameter d and intertible A(X), the Grover walk on X can be "decomposed" into at most d "commuting" continuous quantum walks.
Title: Subdivergencefree gluings of trees
Speaker: Jordan Long Affiliation: University of Waterloo Zoom: Contact Karen YeatsAbstract:
Motivated by questions in quantum field theory, we introduce a purely combinatorial problem of counting subdivergencefree gluings of trees. We present closedform expressions counting subdivergencefree gluings for four different families of trees, as well as an algorithm to count subdivergencefree gluings of arbitrary pairs of trees. This is joint work with Clair Dai and Karen Yeats.
Title: Counting the $c_2$ invariant on the circulant family of graphs
Speaker: Mushegh Shahinyan Affiliation: University of Waterloo Zoom: Contact Karen YeatsAbstract:
The algebrogeometric invariant on Feynman Diagrams called the $c_2$ invariant is a useful tool for detecting properties of Feynman periods. We present this identity on graphs that originate from the scalar $\phi_4$theory with a purely combinatorial perspective and go over some strategies for computing it. We will further narrow our focus onto the circulant family of graphs and present some explicit results.
Title: Abelian covering graphs and their properties
Speaker: Olha Silina Affiliation: University of Waterloo Zoom: Contact Karen YeatsAbstract:
A covering graph is a structure obtained from a graph by ‘replacing’ every vertex with a coclique of size $r$. The main focus of this talk is connections between (spectral) characteristic of a cover and properties such as being walk or distance regular.
Title: What do graph planarity and homomorphism counts have to do with quantum mechanics?
Speaker: David Roberson Affiliation: Technical University of Denmark Zoom: Contact Soffia ArnadottirAbstract:
I will introduce the notion of quantum isomorphisms of graphs. These are defined in terms of a game in which two cooperating players attempt to convince a referee that two given graphs are isomorphic.
Title: Constructing broken SIDH parameters: a tale of De Feo, Jao, and Plut's serendipity.
Speaker: Chloe Martindale Affiliation: University of Bristol Zoom: This event has been cancelled.Abstract:
This talk is motivated by analyzing the security of the cryptographic key exchange protocol SIDH (Supersingular Isogeny DiffieHellman), introduced by 2011 by De Feo, Jao, and Plut. We will first recall some mathematical background as well as the protocol itself. The 'keys' in this protocol are elliptic curves, which are typically described by equations in x and y of the form y^2 = x^3 + ax + b. Of importance in this talk will be 'endomorphisms' associated to elliptic curves: these are functions that map an elliptic curve to itself which also satisfy some nice properties.
Title: State transfer and the size of the graph
Speaker: Gabriel Coutinho Affiliation: Universidade Federal de Minas Gerais Zoom: Contact Soffia ArnadottirAbstract:
If there is perfect state transfer between two vertices at distance d, how small can the graph be compared to d? This question is motivated by the fact that the known infinite families of graphs admitting state transfer at increasingly large distances are all obtained from graph products, thus their sizes grow exponentially compared to their diameter.
Title: An Algorithmic Reduction Theory for Binary Codes: LLL and more
Joint work with Thomas DebrisAlazard and Wessel van Woerden
Speaker: Léo Ducas Affiliation: Centrum Wiskunde & Informatica (CWI) Zoom: Please email Emma WatsonAbstract:
Lattice reduction is the task of finding a basis of short and somewhat orthogonal vectors of a given lattice. In 1985 Lenstra, Lenstra and Lovasz proposed a polynomial time algorithm for this task, with an application to factoring rational polynomials. Since then, the LLL algorithm has found countless application in algorithmic number theory and in cryptanalysis.
Title: Laplacian Quantum Fractional Revival On Graphs
Speakers:Bobae Johnson, August Liu, Malena Schmidt, Neo Yin
Affiliation: York University Zoom: Contact Soffia ArnadottirAbstract:
Given a set of quantum bits, we can model their interactions using graphs. The continuoustime quantum walks on a graph can be viewed as the Schrödinger dynamics of a particle hopping between adjacent vertices. In this talk, the transition matrix of the continuoustime quantum walk is given by $e^{itL}$, where $L$ is the graph’s Laplacian matrix.
Title: Pure pairs
Speaker: Sophie Spirkl Affiliation: University of Waterloo Zoom: Please email Emma Watson.Abstract:
A pure pair in a graph G is a pair of subsets A and B of the vertex set such that between A and B, either all edges or no edges are present in G. This concept was first introduced in connected with the ErdosHajnal conjecture, but has since developed a life of its own. I will give an overview of results and open questions on pure pairs.
Based on joint work with Maria Chudnovsky, Jacob Fox, Alex Scott, and Paul Seymour.
Title: Scaffolds
Speaker: William J. Martin Affiliation: Worcester Polytechnic Institute Zoom: Contact Soffia ArnadottirAbstract:
Building on the work of various authors who have used tensors in the study of association schemes and spin models, I propose the term "scaffold" for certain tensors that have been represented by what are sometimes called "startriangle diagrams" in the literature. The main goal of the talk is to introduce and motivate these objects which somewhat resemble partition functions as they appear in combinatorics. (The exact definition is too cumbersome to include here.)
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 centralized within our Indigenous Initiatives Office.