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November 2023
Atlantic Graph Theory Seminar
Speaker: Jordan Barrett, Toronto Metropolitan University Title: Graph burning, the burning number conjecture, and burning density Abstract: Graph burning is a discrete time process on a graph that acts as a simple model for the spread of social contagion in a network. Graph burning was introduced by Bonato, Janssen and Roshanbin in 2014, and with this introduction came the now famous "burning number conjecture". In the first half of my talk, I will introduce graph burning and give a brief overview of…
Find out more »December 2023
Session on Combinatorial Design Theory at the 2023 Winter Meeting of the Canadian Mathematical Society
Combinatorial design theory has a history dating back to the 18th century when Leonhard Euler pondered the existence of orthogonal pairs of Latin squares. This session will showcase recent results in topics such as classical designs, cycle systems, graph decompositions, Latin squares and other aspects of design theory.
Find out more »Advances in Statistical Modeling of Fisheries Data – Seminar
A Spatiotemporal Model of Condition to Derive a Novel Starvation Mortality Index That Improves a State-space Stock Assessment Model for Atlantic Cod on the Southern Grand Bank of Newfoundland Madhura Weerasekera, Centre for Fisheries Ecosystems Research (CFER), Fisheries and Marine Institute of Memorial University of Newfoundland The Atlantic cod stock on the Southern Grand Bank (SGB) of Newfoundland collapsed in the early 1990's coincident with the collapse of cod stocks across Canadian waters. Consequently, a fishing moratorium has been in place…
Find out more »January 2024
Atlantic Graph Theory Seminar
Speaker: Leslie Hogben, Iowa State University Title: Forts, (fractional) zero forcing, and Cartesian products of graphs Abstract: Zero forcing is an iterative process that repeatedly applies a rule to change the color of vertices of a graph $G$ from white to blue. The zero forcing number is the minimum number of initially blue vertices that are needed to color all vertices blue through this process. Standard zero forcing was introduced about fifteen years ago in the control of…
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Speaker: Torsten Mütze, Un. Warwick Title: Kneser graphs are Hamiltonian Abstract: For integers k>=1 and n>=2k+1, the Kneser graph K(n,k) has as vertices all k-element subsets of an n-element ground set, and an edge between any two disjoint sets. It has been conjectured since the 1970s that all Kneser graphs admit a Hamilton cycle, with one notable exception, namely the Petersen graph K(5,2). This problem received considerable attention in the literature, including a recent solution for the sparsest case…
Find out more »Combinatorial Algebra Meets Algebraic Combinatorics
Combinatorial Algebra Meets Algebraic Combinatorics (CAAC) is a two-day workshop bringing together researchers working at the intersection of combinatorics and algebra. It examines the role of combinatorial structures, such as permutations, matroids and polytopes, arising from problems in Schubert calculus, commutative algebra, and other branches of algebra, representation theory and geometry.
Find out more »Atlantic Graph Theory Seminar
Speaker: Thiago de Holleben, Dalhousie University Title: Homological invariants of graphs with no induced cycles of length divisible by 3 Abstract: If G is a graph with large chromatic number, what can we say about its induced subgraphs? In 2014, Bonamy et al. showed that if a graph has no induced cycles of length divisible by three, then its chromatic number is bounded. Such graphs are called ternary. In an attempt to better understand the structure of the induced subgraphs…
Find out more »February 2024
Atlantic Graph Theory Seminar
Zoom link below. Live viewing for local participants in Chase 227 (tea-drinkers are encouraged to bring their own mug). Speaker: Evelyn Smith-Roberge, Georgia Tech Title:Correspondence Packings of Planar Graphs Abstract: Suppose a graph G has list chromatic number k. It is easy to see that if L is a (k+1)-list assignment for G, then G admits two L-colourings f and g where f(v) =/= g(v) for every vertex v in the graph. But what if we want still more disjoint…
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Speaker: Andrew Beveridge, Macalester College Title: Approval Ballot Triangles Time: Wednesday, February 14, 3.30pm Atlantic time Live viewing for local participants in Chase 227, Dalhousie University Bertrand's Ballot Problem enumerates the number of ways to count ballots so that candidate 1 never trails candidate 2. We generalize this problem by considering an approval ballot election between $n$ candidates. In an approval ballot election, each voter endorses a subset of candidates, rather than voting for just one person. The general approval…
Find out more »Atlantic Graph Theory Seminar
Speaker: Ada Chan, York University Title: Polygamy in state transferAbstract:Let $X$ be a graph and $H$ be a Hermitian matrix associated with $X$. The continuous-time quantum walk with Hamiltonian $H$ isdefined by the time-dependent unitary matrix\begin{equation*}U(t)=e^{i t H}.\end{equation*}Perfect state transfer occurs from vertex $a$ to vertex $b$ at time $\tau$ is $\vert U(\tau)_{b,a}\vert = 1$. This phenomenon is relevant for information transmission in a quantum spin network. For real and symmetric Hamiltonians, it is known that perfect state transfer can…
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