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September 2024

Atlantic Graph Theory Seminar

September 18, 2024 @ 3:30 pm - 4:30 pm
Zoom seminar

Title: How do we use graphs to transmit quantum information? Time: 3.30pm, Atlantic time, (1:30, CDT) Wednesday Sept. 18 Speaker: Hermie Monterde, University of Manitoba Abstract: In this talk, a graph $G$ represents a quantum spin network (a networking of interacting subatomic particles). The vertices and edges of $G$ represent the particles and their interactions in the network. Consider the complex unitary matrix $U(t)=\exp(itA)$, where $A$ is the adjacency matrix of $G$, $i^2=-1$ and $t$ is a real number. The propagation of quantum…

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Atlantic Graph Theory Seminar

September 25, 2024 @ 3:00 pm - 4:30 pm
Online via Zoom

Recolouring Graphs: Decompositions, A Dichotomy Theorem and Frozen   Colourings Speaker: Kathie Cameron, Wilfrid Laurier University A k-colouring of a graph G is an assignment of at most k colours to the vertices of a graph so that the ends of each edge of the graph get different colours. We consider the question: When it is possible to obtain any k-colouring from any other by changing the colour of one vertex at a time, while always having a k-colouring? This question is equivalent to asking whether the “reconfiguration…

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October 2024

Atlantic Graph Theory Seminar

October 2, 2024 @ 3:30 pm - 4:30 pm
Online via Zoom

The Martin Invariant and Other Results on the Interlace Polynomials Josephine Reynes, University of Waterloo There are many well studied graph polynomials, but this talk will focus on the Martin polynomial and the interlace polynomial. Specifically, this talk will look at how these two polynomials are related and how results on the Martin polynomial can be extended to the interlace polynomial. The Martin invariant, a specific evaluation of the Martin polynomial, obeys the symmetries of the Feynman period. The Feynman…

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Atlantic Graph Theory Seminar

October 23, 2024 @ 3:30 pm - 4:30 pm
Online via Zoom

Speaker #1: Peter Collier, Dalhousie University Title #1: Zero Forcing on Twisted Hypercubes Abstract #1: The hypercube stands out as a compelling and versatile structure that extends the geometric notion of a cube into higher dimensions. We study the twisted hypercube variant in an attempt to optimize processes on similarly degree-regular, highly connected graphs. The particular process we optimize is zero forcing, a graph infection process in which a particular colour change rule is iteratively applied to the graph and an…

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November 2024

Atlantic Graph Theory Seminar

November 6, 2024 @ 3:30 pm - 4:30 pm
Online via Zoom

On the two table case of the directed Oberwolfach problem Speaker: Alice Lacaze-Masmonteil, University of Regina A directed variant of the famous Oberwolfach problem, the directed Oberwolfach problem considers the following scenario. Given n people seated at t round tables of size m1,m2 . . . ,mt , respectively, such that m1+m2+· · ·+mt = n, does there exist a set of n−1 seating arrangements such that each person is seated to the right of every other person precisely once?…

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Atlantic Graph Theory Seminar

November 27, 2024 @ 3:30 pm - 4:30 pm
Online via Zoom

Speaker: Iain Beaton, Acadia University Title: Reconfiguring minimal dominating sets under a generalization of token sliding Abstract: A dominating set S in a graph is a subset of vertices such that every vertex is either in S or adjacent to a vertex in S. A minimal dominating set M is a dominating set such that M −v is not a dominating set for all v ∈ M. In this talk we introduce a reconfiguration graph R(G) for minimal dominating sets…

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January 2025

Atlantic Graph Theory Seminar

January 15, 2025 @ 3:30 pm - 4:30 pm
Online via Zoom

Speakers: Prangya Parida, U. Ottawa, and Kiara McDonald, U. Victoria Zoom link:  https://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09 --------------------------------------------------- Prangya Parida: Title: Cover-free families on graphs Abstract: A family of subsets of a t-set is called a d-cover-free family if no subset is contained in the union of any d other subsets. We denote by t(d, n) the minimum  t for which there exists a d-cover-free family of a t-set with n subsets. Cover-free families (CFF) have wide applications in combinatorial group testing, where a d-CFF(t, n) can be…

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Atlantic Graph Theory Seminar

January 22, 2025 @ 3:30 pm - 4:30 pm
Online via Zoom

Ramsey numbers of signed graphs Ben Seamone, Dawson College and Université de Montréal Abstract: Nathan Acheampong (Université de Montréal) Francis Clavette (Université de Montréal) Geˇna Hahn (Université de Montréal) Margaux Marseloo (Université Paris-Saclay) Viktor Paardekooper (Université de Montréal), and Ben Seamone* (Dawson College & Université de Montréal) A signed graph is a pair (G, σ) where G = (V,E) is a graph and σ : E(G) → {+, −} is a signature which assigns a sign to each edge of G. One well-studied operation on…

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Atlantic Graph Theory Seminar

January 29, 2025 @ 3:30 pm - 4:30 pm
Online via Zoom

Switching m-edge coloured graphs Speaker: Gary MacGillivray, University of Victoria Abstract: An m-edge-coloured graph consists of a set of vertices, any two of which are either joined by an edge of one of m colours or not joined at all. The operation of switching at a vertex v of an m-edge-coloured graph with respect to an element of a subgroup \Gamma of S_m  permutes the colours of the edges incident with v.  Switching defines an equivalence relation on the set…

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February 2025

Atlantic Graph Theory Seminar

February 5, 2025 @ 3:30 pm - 4:30 pm
Online via Zoom

Kemeny's constant for Markov chains and random walks on graphs Speaker: Jane Breen, Ontario Tech University Kemeny's constant is an interesting and useful quantifier of how well-connected the states of a Markov chain are. Though it was first introduced in the 1960s, interest in this concept has recently exploded. This talk will provide an introduction to Markov chains, an overview of the history of Kemeny’s constant, discussion of some applications, and a survey of recent results, with an emphasis on…

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