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TZID:UTC
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DTSTART:20220101T000000
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BEGIN:VEVENT
DTSTART;TZID=UTC:20250326T153000
DTEND;TZID=UTC:20250326T163000
DTSTAMP:20260610T222828
CREATED:20250319T205857Z
LAST-MODIFIED:20250319T205857Z
UID:8166-1743003000-1743006600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:The Burning Number of Large Caterpillars \nDanielle Cox\, Mount Saint Vincent University \nAbstract:\nIn this talk we will look at the history of the graph burning conjecture and the state of the art. We will also prove the conjecture for sufficiently large p-caterpillars. This is joint work with Kerry Ojakian (CUNY) and Margaret-Ellen Messinger (Mt Allison).\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-30/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250319T153000
DTEND;TZID=UTC:20250319T163000
DTSTAMP:20260610T222828
CREATED:20250313T101400Z
LAST-MODIFIED:20250313T101400Z
UID:8039-1742398200-1742401800@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:The 2-burning number of a graph\nSpeaker: Ann Trenk\, Wellesley College\n\nAbstract:\nWe discuss a discrete-time model for the spread of information in a graph\, motivated by the idea that people believe a story when they learn of it from two different origins. Similar to the burning number\, in this problem\, information spreads in rounds and a new source can appear in each round. For a graph $G$\, we are interested in $b_2(G)$\, the minimum number of rounds until the information has spread to all vertices of graph $G$. We are also interested in finding $t_2(G)$\, the minimum number of sources necessary so that the information spreads to all vertices of $G$ in $b_2(G)$ rounds. In addition to discussing general results\, we find $b_2(G)$ and $t_2(G)$ for the classes of spiders and wheels and show that their behavior differs with respect to these two parameters.\n\nThis is joint work with Catherine Jacobs (Wellesley College) and Margaret-Ellen Messinger (Mount Allison University).\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-29/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250312T153000
DTEND;TZID=UTC:20250312T163000
DTSTAMP:20260610T222828
CREATED:20250305T143502Z
LAST-MODIFIED:20250305T143502Z
UID:7955-1741793400-1741797000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Time: 3:30 pm\, Atlantic time\, (2:30 pm EST) Wednesday\, Mar. 12\nSpeaker: Ron Gould\, Emory University\nTitle: Looking for Saturation in all Kinds of Places\n\nAbstract:\nGiven a graph $H$\, a graph $G$ is $H$-saturated if $G$ does not contain $H$ as a subgraph\, but the addition of any missing edge to $G$ results in a graph containing $H$ as a subgraph. An $H$-saturated graph with the maximum number of edges is called an extremal graph for $H$ and for a given order $n$ we denoted this as $\ext(n\, H).$   This is the well-known extremal number (or Turan number) of $H$ and is a well studied notion with a deep and beautiful history.\n\nHowever\, the focus of this talk will be the many other saturation questions that can be asked.   These include what is the minimum number of edges in an $H$-saturated graph?  What sizes (i.e. $|E(G)|$)\, other than the minimum or maximum\, also allow $H$-saturated graphs on $n$ vertices?   Is it possible to order the inclusion of the missing edges so that at each stage more copies of $H$ will be included? What about saturation in other settings such as in hypergraphs\, edge-colored graphs\, random graphs\, or within graphs other than the complete graph?\n\nKeywords: saturation\, saturation spectrum\, weak saturation\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-28/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250226T153000
DTEND;TZID=UTC:20250226T163000
DTSTAMP:20260610T222828
CREATED:20250220T195135Z
LAST-MODIFIED:20250220T195135Z
UID:7949-1740583800-1740587400@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Karen Meagher\, University of Regina\nTitle: Derangement graphs and the intersection density of permutation groups\n\nAbstract:\nTwo permutations are intersecting if they both map some $i$ to the same point\, equivalently\, permutations $\sigma$\nand $\pi$ are intersecting if and only if $\pi^{-1}\sigma$ has a fixed point. A set of permutations is called intersecting if any two permutations in the set are intersecting. For any transitive group the stabilizer of a point is an intersecting set. The intersection density of a permutation group is the ratio of the size of the largest intersecting set in the group\, to the size of the stabilizer of a point. If the intersection density of a group is 1\, then the stabilizer of a point is an intersecting set of maximum size. Such groups are said to have the Erd\H{o}s-Ko-Rado property.\n\nOne effective way to determine the intersection density of a group is build a graph whose vertices are the elements of the group and the edges are defined so that the cocliques (or the independent sets) in the graph are exactly the intersecting sets in the group. This graph is called the derangement graph for the group. The focus on this talk is to demonstrate several ways we can use the derangement graph to find the intersection density of a group.\n\nAn easy example of how this can be done is if the graph has a clique with the size of the degree of the group\, then the group has intersection density 1. We can also use graph homomorphisms to find bounds on the intersection density. For many small groups\, the derangement graph has a very simple form and the intersection density of the group can be easily found simply from the structure of the derangement graph. In a surprising number of cases\, eigenvalues of the derangement graph can be found using the representation theory of the group and\, using tools from algebraic graph theory\, these eigenvalues can be used to bound the size of a coclique.\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-27/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250212T153000
DTEND;TZID=UTC:20250212T163000
DTSTAMP:20260610T222828
CREATED:20250211T123857Z
LAST-MODIFIED:20250211T124101Z
UID:7937-1739374200-1739377800@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Time: 3:30 pm\, Atlantic time\, (4:00 pm NST) Wednesday\, Feb. 12\nSpeaker: Robert Bailey\, Memorial University\nTitle: Computer constructions of distance-regular graphs with primitive automorphism groups\n\nAbstract:\nA graph is distance-regular if\, for each vertex $v$ and each vertex $w$ at distance $i$ from $v$\, the number of neighbours of $w$ at distances $i-1$\, $i$ or $i+1$ from $v$ depends only on $i$\, and not on the choice of $v$ or $w$.  These are highly-structured graphs with interesting structural and algebraic properties.  Many of the well-known examples have large symmetry groups.\n\nThe GAP computer algebra system contains libraries of primitive permutation groups (i.e. those which preserve no interesting equivalence relations).  With the assistance of my undergraduate research students\, I have been analyzing these libraries with the ultimate aim of classifying the distance-regular graphs with such groups as automorphism groups.  In this talk\, I will discuss the status of this work\, a few surprises which came up along the way\, and some (theoretical and computational) questions which remain open.\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-26/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250205T153000
DTEND;TZID=UTC:20250205T163000
DTSTAMP:20260610T222828
CREATED:20250130T120621Z
LAST-MODIFIED:20250130T120621Z
UID:7934-1738769400-1738773000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Kemeny’s constant for Markov chains and random walks on graphs\nSpeaker: Jane Breen\, Ontario Tech University\n\nKemeny’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 those where the combinatorial structure of the Markov chain is of interest. This comes to the forefront when the Markov chain in question is a random walk on a graph\, in which case Kemeny’s constant is interpreted as a measure of how `well-connected’ the graph is.\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-25/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250129T153000
DTEND;TZID=UTC:20250129T163000
DTSTAMP:20260610T222828
CREATED:20250124T114752Z
LAST-MODIFIED:20250124T115307Z
UID:7921-1738164600-1738168200@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Switching m-edge coloured graphs\nSpeaker: Gary MacGillivray\, University of Victoria\n\nAbstract:\n\nAn 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 of all m-edge-coloured graphs;  G and H are \Gamma-switch-equivalent if there exists a sequence of switches that transform G into H. \nWe consider the following problems and their solutions.  For a fixed subgroup \Gamma of S_m:\n1) determine the number of equivalence classes of k-vertex m-edge-coloured graphs under switching with respect to \Gamma.\n2) how hard is it to determine whether given m-edge-coloured graphs G and H are \Gamma-switch equivalent?\n3) for a fixed m-edge-coloured graph H\, how hard is it to determine whether a given m-edge-coloured graph G can be switched with respect to \Gamma so that there is a homomorphism of the transformed m-edge-coloured graph to H?  (A homomorphism is a mapping of V(G) to V(H) that preserves edges and colours.) \nWe will also discuss extending these results to (m\,n)-mixed graphs.  These have m different colours of edges and n different colours of arcs. \n\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-24/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250122T153000
DTEND;TZID=UTC:20250122T163000
DTSTAMP:20260610T222828
CREATED:20250118T104832Z
LAST-MODIFIED:20250118T104832Z
UID:7875-1737559800-1737563400@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Ramsey numbers of signed graphs\nBen Seamone\, Dawson College and Université de Montréal\n\nAbstract:\nNathan Acheampong (Université de Montréal) Francis Clavette (Université de Montréal)\nGeˇna Hahn (Université de Montréal) Margaux Marseloo (Université Paris-Saclay) Viktor\nPaardekooper (Université de Montréal)\, and Ben Seamone* (Dawson College & Université de Montréal)\n\nA signed graph is a pair (G\, σ) where G = (V\,E) is a graph and σ : E(G) → {+\, −} is\na signature which assigns a sign to each edge of G. One well-studied operation on signed\ngraphs is that of switching at a vertex v ∈ V (G)\, by which we mean that every edge incident\nto v has its sign changed. Two signed graphs are called equivalent if one can be obtained\nfrom the other by a sequence of vertex switches.\n\nWe call a complete signed graph positive (negative) if every edge is positive (negative). We\nstudy the following Ramsey problem on signed graphs – for positive integers s and t\, what\nis the smallest n such that every signed complete graph on n vertices has an equivalent\nsigned complete graph containing either a negative Ks or positive Kt? This “signed Ramsey\nnumber” is denoted r±(s\, t). We show how a variety of approaches lead to upper and lower\nbounds on r±(s\, t)\, settle an open problem by establishing the exact value of r±(4\, t) for\nevery t\, and determine the asymptotics of r±(5\, t) and r±(6\, t).\n \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-23/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250115T153000
DTEND;TZID=UTC:20250115T163000
DTSTAMP:20260610T222828
CREATED:20250110T114756Z
LAST-MODIFIED:20250110T114821Z
UID:7869-1736955000-1736958600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speakers: Prangya Parida\, U. Ottawa\, and Kiara McDonald\, U. Victoria\nZoom link:  https://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\n—————————————————\nPrangya Parida:\nTitle: Cover-free families on graphs\n\nAbstract: 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 used to identify d defective items in a group of n items with t tests. It is well-known that t(1\, n) can be obtained by applying the famous Sperner’s Theorem. For d \geq 2\, we rely on bounds for t(d\, n).  Erdös\, Frankl\, and Füredi provided bounds for t(2\, n) using the probabilistic method\, given by 3.106 \log(n) < t(2\, n) < 5.512 \log(n). Using a derandomization technique\, Porat and Rothschild presented a deterministic polynomial-time algorithm to construct d-CFFs that achieves t = O(d^2 \log(n)). Some upper bounds on t(2\, n) (in some cases exact bounds) for small values of n are provided by Li\, van Rees\, and Wei in 2006.\n   In this talk\, we extend the definition of a cover-free family to include a graph G\, which we denote as \overline{G}-CFF\, where the edges of the graph specify the pair of subsets whose union must not cover any other subset. We denote by t(G)  the minimum t for which there exists a \overline{G}-CFF. The traditional 2-CFF(t\, n) is a special case of \overline{G}-CFF when G  is a complete graph of n vertices. This generalization of cover-free families provides a richer combinatorial structure  that lies between being a 1-CFF and a 2-CFF.\n   We will discuss some classical results on cover-free families\, along with general constructions of \overline{G}-CFFs\, as well as specific constructions for certain families of graphs. We prove that for a graph G with n vertices\,  t(1\, n) \leq t(G) \leq t(2\, n) and show that for an infinite family of Star graphs S_n with n vertices\, t(S_n) = t(1\, n). Interestingly\, we also give a construction of CFFs on a Path (P_n) or Cycle (C_n) with n vertices using a mixed-radix Gray code. This yields an upper bound for t(P_n) and t(C_n) that is smaller than the lower bound of t(2\, n) mentioned above.\n   This is joint work with Lucia Moura.\n\n——————————————————\nKiara McDonald:\nTitle: Broadcast Independence in Trees\n\n\nAbstract: In the area of Graph Theory\, the well-known problems of domination\, packing and independence are generalized by broadcast domination\, broadcast packing and broadcast independence. As an analogy and application\, consider a city\, where one wants to place cell towers of different signal strengths subject to certain conditions. If every building in the city hears the signal from at least (respectively at most) one tower\, then the broadcast is dominating (respectively  packing). If no tower hears the signal from another tower\, the broadcast is independent. The sum of the tower signal strengths is called the cost of the broadcast. The total cost of a maximum independent broadcast is called the broadcast independence number. \nOur research was focused on determining explicit formulas and polynomial time algorithms for the broadcast independence number of various types of graphs. This parameter is difficult to compute for graphs in general\, so we restrict the problem to specific classes of graphs to make use of their special structural properties to solve the problem. For a graph from a given class\, we constructed a new graph\, called the broadcast ball intersection graph. We were able to show that if the broadcast ball intersection graph is weakly chordal\, then broadcast independence is polynomial time solvable for the given class of graphs. In this talk\, we will focus on the broadcast ball intersection graph of trees. This talk is based on joint work with Richard Brewster (TRU) and Jing Huang (UVic).
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-22/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20241127T153000
DTEND;TZID=UTC:20241127T163000
DTSTAMP:20260610T222828
CREATED:20241121T122556Z
LAST-MODIFIED:20241121T122556Z
UID:7806-1732721400-1732725000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Iain Beaton\, Acadia University\nTitle: Reconfiguring minimal dominating sets under a generalization of token sliding\n\nAbstract:\nA 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 under a generalization of the token sliding model. We give some preliminary results which include showing that R(G) is connected for trees and split graphs. Additionally we classify all graphs which have complete or empty reconfiguration graphs.\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-21/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20241106T153000
DTEND;TZID=UTC:20241106T163000
DTSTAMP:20260610T222828
CREATED:20241101T102124Z
LAST-MODIFIED:20241101T102807Z
UID:7778-1730907000-1730910600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:On the two table case of the directed Oberwolfach problem\nSpeaker: Alice Lacaze-Masmonteil\, University of Regina\n\nA directed variant of the famous Oberwolfach problem\, the directed Oberwolfach problem considers\nthe following scenario. Given n people seated at t round tables of size m1\,m2 . . . \,mt \, respectively\,\nsuch that m1+m2+· · ·+mt = n\, does there exist a set of n−1 seating arrangements such\nthat each person is seated to the right of every other person precisely once? I will first demonstrate\nhow this problem can be formulated as a type of graph-theoretic problem known as a cycle decomposition\nproblem. Then\, I will discuss a particular style of construction that was first introduced\nby R. Häggkvist in 1985 to solve several cases of the original Oberwolfach problem. Lastly\, I will\nshow how this approach can be adapted to the directed Oberwolfach problem\, thereby allowing\nus to obtain solutions for previously open cases. Certain results discussed in this talk arose from\ncollaboration with Daniel Horsley.\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-20/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20241023T153000
DTEND;TZID=UTC:20241023T163000
DTSTAMP:20260610T222828
CREATED:20241018T101206Z
LAST-MODIFIED:20241018T101259Z
UID:7744-1729697400-1729701000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker #1: Peter Collier\, Dalhousie University\nTitle #1: Zero Forcing on Twisted Hypercubes\n\nAbstract #1:\nThe 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 initial set of vertices. We use the alternative framing  of forcing arc sets to construct a family of twisted hypercubes of dimension k$\geq3$ with zero forcing sets of size $2^{k-1}-2^{k-3}+1$.\n\n\nSpeaker #2: Alexander Clow\, Simon Fraser University\nTitle #2: Cornering Robots and Synchronizing Automata\n\n\nAbstract #2:\nA deterministic finite automata (DFA) is a model for any deterministic computational system with a finite number of states. In this talk\, we describe a DFA as a finite directed multigraph G = (V\, E)\, possibly with loops\, along with an edge labelling ψ : E → Ψ. Here the vertices of the graph are the states the system might be in\, the edge labels are possible inputs to the system\, and the edges represent the transitions between states. Words σ generated from the alphabet Ψ act on vertices\, v\, as if v is the initial state of the system\, and σ(v) is the state of the system after input σ is given. A word σ is synchronizing if for all u\, v ∈ V \, σ(u) = σ(v).\nIn this talk\, we define a general strategy for constructing synchronizing words\, which we call the cornering strategy. We then show that a DFA is synchronizable if and only if the cornering strategy can be successfully applied. As a demonstration of the strategy\, we will discuss how all DFAs arising from movement in Rd can be synchronized. This is joint work with Peter Bradshaw (University of Illinois Urbana-Champaign) and Ladislav Stacho (Simon Fraser University).\n\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-18/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20241002T153000
DTEND;TZID=UTC:20241002T163000
DTSTAMP:20260610T222828
CREATED:20240928T105843Z
LAST-MODIFIED:20240928T105843Z
UID:7719-1727883000-1727886600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:The Martin Invariant and Other Results on the Interlace Polynomials \nJosephine Reynes\, University of Waterloo \nThere 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 period of a graph is useful in quantum field theory\, but difficult to compute and thus there is interest in finding graph invariants that have the same symmetries. It was quickly established that the interlace polynomial on interlace graphs was equal to the Martin polynomial on the associated 4-regular graph. While only graphs not containing a set of forbidden vertex minors are interlace graphs\, the interlace polynomial is defined over all graphs. We discuss how this provides a way to try and extend the notion of Feynman symmetries via the interlace polynomial and some specific classes of graphs with formulas. Additionally\, the interlace polynomial is only equal to the Martin polynomial for interlace graphs of 4-regular graphs\, but the Martin polynomial is defined for 2k-regular graphs. Thus\, we work toward creating an interlace-like polynomial for graphs derived from 2k-regular cases of the Martin polynomial. \nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1 \nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-17/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240925T150000
DTEND;TZID=UTC:20240925T163000
DTSTAMP:20260610T222828
CREATED:20240925T124502Z
LAST-MODIFIED:20240925T124502Z
UID:7696-1727276400-1727281800@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Recolouring Graphs: Decompositions\, A Dichotomy Theorem and Frozen   Colourings \nSpeaker: Kathie Cameron\, Wilfrid Laurier University \nA 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 graph” is connected: The reconfiguration graph of the k-colourings\, denoted Rk(G)\, is the graph whose vertices are the k-colourings of G\, and two colourings are adjacent in Rk(G) if they differ in colour on exactly one vertex. We call a graph recolourable if Rk(G) is connected for every k greater than its chromatic number.\n\nWe have characterized the graphs H such that all graphs G which don’t contain H as an induced subgraph are recolourable. We have done the same when two 4-vertex graphs are excluded as induced subgraphs (except for one class) and for some classes of graphs which exclude as an induced subgraph the path on 5 vertices.\n\nDecompositions are important in solving optimization problems on structured classes of graphs. We have shown that modular decomposition and a stronger version of clique cutsets which we call tight clique cutsets can be used to show that certain classes are recolourable.\n\nA k-colouring of a graph is called frozen if there is no vertex whose colour can be changed so that the result is still a k-colouring. A frozen colouring corresponds to an isolated vertex of the reconfiguration graph\, and thus the existence of a frozen colouring is one way to show that a class of graphs is not recolourable. We have found several new classes of graphs with frozen colourings and an operation which transforms a k-chromatic graph with a frozen (k+1)-colouring into a (k+1)-chromatic graph with a frozen (k+2)-colouring.\nThis is joint work with Manoj Belavadi\, Elias Hildred\, Owen Merkel and Dewi Sintiari.\n\n\nZoom link:\nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1\n\nMeeting ID: 868 6149 9971\nPasscode: 325258
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-16/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240918T153000
DTEND;TZID=UTC:20240918T163000
DTSTAMP:20260610T222828
CREATED:20240915T122521Z
LAST-MODIFIED:20240915T122521Z
UID:7672-1726673400-1726677000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Title: How do we use graphs to transmit quantum information? \nTime: 3.30pm\, Atlantic time\, (1:30\, CDT) Wednesday Sept. 18 \nSpeaker: Hermie Monterde\, University of Manitoba \nAbstract: \nIn 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 states in the quantum system determined by $G$ is governed by the matrix $U(t)$. In particular\, $|U(t)_{u\,v}|^2$ may be interpreted as the probability that the quantum state assigned at vertex $u$ is transmitted to vertex $v$ at time $t$. In this talk\, we give an overview of the study of quantum state transfer in graphs. We discuss old and new results in this area with emphasis on the concepts and techniques borrowed from graph theory and linear algebra. \n\nZoom link: \nhttps://us02web.zoom.us/j/86861499971?pwd=rTDAaju0TCu24asnaBGvkuNlT11KZ1.1
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-15/
LOCATION:Zoom seminar
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240306T153000
DTEND;TZID=UTC:20240306T163000
DTSTAMP:20260610T222828
CREATED:20240301T112625Z
LAST-MODIFIED:20240301T112625Z
UID:7577-1709739000-1709742600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Induced subgraphs and treewidth\nSpeaker: Sophie Spirkl\, University of Waterloo\nAbstract: Treewidth is a measure of the complexity of a graph and has both structural and algorithmic consequences. While results of Robertson and Seymour characterize which minors appear in graphs of large treewidth\, the same question is still open for induced subgraphs. I will present some recent results towards an answer to this question\, in particular\, about when excluding a finite set of induced subgraphs leads to the answer being “what we expect”. Joint work with Bogdan Alecu\, Maria Chudnovsky\, and Sepehr Hajebi. \n\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547\n\n\nLive viewing with refreshments in Chase 227\, Dalhousie University (bring your own mug for tea.)
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-14/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240228T153000
DTEND;TZID=UTC:20240228T163000
DTSTAMP:20260610T222828
CREATED:20240228T114600Z
LAST-MODIFIED:20240228T114626Z
UID:7574-1709134200-1709137800@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Pursuit-evasion on Graphs\nTrent Marbach\, Toronto Metropolitan University \nThe study of pursuit-evasion on graphs looks at games played between two adversaries\, with one player tasked with alluding capture from the other on the graph. We will describe these types of games in general\, although we will take a particular focus on two games: the Cops and Robber game\, and the Localization game. A famous open conjecture for the Cops and Robber game has spurred recent work in the area\, and we show how this work connects to various graph theory topics\, including isoperimetry\, network search\, and width parameters. We will also provide some new applications that have resulted from this work. \nLive viewing at Dalhousie in Chase 227 (bring your own mug for tea). \n——————————\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-13/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240221T153000
DTEND;TZID=UTC:20240221T163000
DTSTAMP:20260610T222828
CREATED:20240219T131416Z
LAST-MODIFIED:20240219T131514Z
UID:7556-1708529400-1708533000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Ada Chan\, York University\nTitle: 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 occur from a vertex to at most one other vertex\,mand that graphs with perfect state transfer are rare.    A relaxation\, called pretty good state transfer\, occurs from $a$ to $b$ if $\vert U(\tau)_{b\,a}\vert$ gets arbitrarily close one.  Pal and Bhattacharjya discover a graph with four vertices admitting pairwise pretty good state transfer. In this talk\, we present a family of graphs that admit pairwise pretty good state transfer in an arbitrarily large set of vertices. We compare this polygamous behaviour to walks with Hamiltonians that contain non-real entries.\n\n\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-12/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240214T153000
DTEND;TZID=UTC:20240214T163000
DTSTAMP:20260610T222828
CREATED:20240211T201100Z
LAST-MODIFIED:20240211T201216Z
UID:7549-1707924600-1707928200@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Andrew Beveridge\, Macalester College\nTitle: Approval Ballot Triangles\nTime: Wednesday\, February 14\, 3.30pm Atlantic time\nLive viewing for local participants in Chase 227\, Dalhousie University\n \nBertrand’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 ballot problem becomes: how many ways can the ballots be counted so that candidate $k$ never trails candidate $k+1$? This formulation yields a family of binary triangular arrays\, called approval ballot triangles (ABTs)\, that are in bijection with totally symmetric self-complementary plane partitions. We show that ABTs unify three different TSSCPP families of triangular arrays. We then further the connection between TSSCPPs and ballot problems by giving a decomposition of a strict-sense ballot into a list of sequentially compatible ABTs\n \nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n \nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-11/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240206T153000
DTEND;TZID=UTC:20240206T163000
DTSTAMP:20260610T222828
CREATED:20240205T201726Z
LAST-MODIFIED:20240205T201815Z
UID:7536-1707233400-1707237000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Zoom link below. Live viewing for local participants in Chase 227 (tea-drinkers are encouraged to bring their own mug).\n \nSpeaker: Evelyn Smith-Roberge\, Georgia Tech\nTitle:Correspondence Packings of Planar Graphs\n \nAbstract: 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 L-colourings without making our lists too big? In this talk\, I will discuss recent progress towards determining the list packing number of various classes of planar graphs: that is\, the smallest number k such that if L is a k-list assignment for an arbitrary graph G in the class under study\, then L can be decomposed into k disjoint L-colourings. All results I will discuss also hold in the correspondence colouring framework. Joint work with Daniel Cranston.\n \nJoin ZOOM Meeting:\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-10/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240131T153000
DTEND;TZID=UTC:20240131T163000
DTSTAMP:20260610T222828
CREATED:20240127T122401Z
LAST-MODIFIED:20240127T122513Z
UID:7485-1706715000-1706718600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Thiago de Holleben\, Dalhousie University\nTitle: Homological invariants of graphs with no induced cycles of length divisible by 3\n \nAbstract:  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.\nIn an attempt to better understand the structure of the induced subgraphs of a graph with bounded chromatic number\, Kalai and Meshulam posed questions relating topological invariants of the independence complex\, and the chromatic number of a graph. Since then\, there have been several results bounding chromatic numbers of graphs using topology. In 2022\, Jinha Kim showed a conjecture of Engström stating the exact topological structure of the independence complex of a ternary graph. In this talk\, we describe a graph theoretic way of computing this structure. As an application\, we show that -1 is a root of the independence polynomial of a forest F if and only if the induced matching number of F is not equal to the domination number of F.\n \nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-9/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240124T153000
DTEND;TZID=UTC:20240124T163000
DTSTAMP:20260610T222828
CREATED:20240118T184108Z
LAST-MODIFIED:20240118T184230Z
UID:7478-1706110200-1706113800@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Torsten Mütze\, Un. Warwick\nTitle: Kneser graphs are Hamiltonian\n  \nAbstract: 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 n=2k+1. The main contribution of our work is to prove the conjecture in full generality. We also extend this Hamiltonicity result to all connected generalized Johnson graphs (except the Petersen graph). The generalized Johnson graph J(n\,k\,s) has as vertices all k-element subsets of an n-element ground set\, and an edge between any two sets whose intersection has size exactly s. Clearly\, we have K(n\,k)=J(n\,k\,0)\, i.e.\, generalized Johnson graphs include Kneser graphs as a special case. Our results imply that all known families of vertex-transitive graphs defined by intersecting set systems have a Hamilton cycle\, which settles an interesting special case of Lovász’ conjecture on Hamilton cycles in vertex-transitive graphs from 1970. Our main technical innovation is to study cycles in Kneser graphs by a kinetic system of multiple gliders that move at different speeds and that interact over time\, reminiscent of the gliders in Conway’s Game of Life\, and to analyze this system combinatorially and via linear algebra.\n  \nThis is joint work with my students Arturo Merino (TU Berlin) and Namrata (Warwick).\n\n———————————————————\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-8/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20240117T153000
DTEND;TZID=UTC:20240117T163000
DTSTAMP:20260610T222828
CREATED:20240110T181847Z
LAST-MODIFIED:20240110T182517Z
UID:7474-1705505400-1705509000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker:  Leslie Hogben\, Iowa State University\nTitle:         Forts\, (fractional) zero forcing\, and Cartesian products of graphs\n\nAbstract: 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 quantum systems and as an upper bound for  maximum multiplicity of an eigenvalue (or maximum nullity) among matrices having off-diagonal nonzero pattern described by the edges of the graph $G$\, and rediscovered later both as part of power domination and as fast-mixed graph searching.\n\nWhether a set is a zero forcing set can be tested using a certain type of set called a fort\, which obstructs zero forcing.   The maximum number of disjoint forts (fort number)  provides another  lower bound for the zero forcing number; results about fort number will be discussed.  Forts can be used in integer programs to determine the zero forcing number and fort number.  The relaxation of these integer programs leads to dual linear programs that define the fractional zero forcing number\, or equivalently\, the fractional fort number\, and results about these parameters will be discussed.\n\nThere is a well-known upper bound for the zero forcing number of a Cartesian product in terms of the zero forcing numbers and orders of the constituent graphs.  The question of a lower bound for the zero forcing number of a Cartesian product has recently been studied.  It is easy to see that there is a Vizing-like lower bound when the constituent graphs of the Cartesian product both have maximum nullity equal to zero forcing number.  Fractional zero forcing and fort number provide additional lower bounds on the the zero forcing number of a Cartesian product in terms of parameters of the constituent graphs.\n\n______________________________________________________________________________\nJeannette Janssen is inviting you to a scheduled Zoom meeting.\n\nTopic: Atlantic Graph Theory Seminar\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-leslie-hogben/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20231129T153000
DTEND;TZID=UTC:20231129T163000
DTSTAMP:20260610T222828
CREATED:20231124T122206Z
LAST-MODIFIED:20231124T122206Z
UID:7462-1701271800-1701275400@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Jordan Barrett\, Toronto Metropolitan University\nTitle: Graph burning\, the burning number conjecture\, and burning density \nAbstract: 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 the progress made towards the burning number conjecture. Then\, for the remainder of the talk\, I will introduce a variation of graph burning in which the graph grows over time. In this variation\, if the graph grows fast enough then we may never be able to burn all of the vertices at any given time. We are instead interested in the “burning density”\, i.e.\, the limiting ratio of burning vertices to all vertices. The talk will conclude with some new results by Gunderson\, Nir\, Pralat\, and myself\, classifying the obtainable burning densities on growing grid-graphs. \nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-7/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20231122T153000
DTEND;TZID=UTC:20231122T163000
DTSTAMP:20260610T222828
CREATED:20231118T113007Z
LAST-MODIFIED:20231118T113007Z
UID:7454-1700667000-1700670600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker:  Santiago Guzman-Pro\, TU Dresden\nTitle:          Forbidden Tournaments and the Orientation (Completion) Problem\n\nAbstract:   For a fixed finite set of  oriented graphs F\,  the F-free  orientation problem asks\nwhether a given finite undirected graph G has an F-free orientation\, i.e.\, whether the edges\nof  G  can be  oriented so that the  resulting  oriented  graph does not contain  any oriented\ngraph from F as an oriented (induced) subgraph. It was first noted by Bang-Jensen\, Huang\,\nand Prisner that when F is a set of oriented paths on 3 vertices\, this problem easily reduces\nto 2-SAT\, and thus is solvable in polynomial-time. This was later extended to sets of oriented\ngraphs on 3 vertices (G.P.\ and Hernández-Cruz 2017). Towards a complete understanding\nof the complexity of the F-free orientation problem\,  we consider the case when  F is a set of\nfinite  tournaments.     We prove that  for every  such  F\,  this problem is in P or NP-complete.Specifically\, we show that either the F-free orientation problem can be reduced (in polynomial-\ntime) to a system of Boolean linear equations\, or the F-free orientation problem is NP-complete.\nThis  dichotomy result is  accompanied  by a  classification  statement  which\, given a set of\ntournaments  F\,   allows  us  to decide  whether  the  F-free  orientation  problem  is in  P  or\nNP-complete. We reduce this classification task to a complete complexity classification of the\norientation completion problem for F\, which is the variant of the problem above where the input\nis a partially oriented graph instead of an undirected graph\, introduced by Bang-Jensen\, Huang\,\nand Zhu (2017). Our proof uses results from the theory of constraint satisfaction\, and a result\nof Agarwal and Kompatscher (2018) about infinite permutation groups and transformation monoids.\n\nThis is joint work with Manuel Bodirsky.
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-6/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20231101T153000
DTEND;TZID=UTC:20231101T163000
DTSTAMP:20260610T222828
CREATED:20231028T105516Z
LAST-MODIFIED:20231028T105516Z
UID:7402-1698852600-1698856200@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Detecting (Di)Graphical Regular Representations \nSpeaker: Joy Morris\, U. Lethbridge \nAbstract: Graphical and Digraphical Regular Representations (GRRs and DRRs) are a concrete way to visualise the regular action of a group\, using (di)graphs. More precisely\, a GRR or DRR on the group $G$ is a (di)graph whose automorphism group is isomorphic to the regular action of $G$ on itself by right-multiplication.\n\nFor a (di)graph to be a DRR or GRR on $G$\, it must be a Cayley (di)graph on $G$. Whenever the group $G$ admits an automorphism that fixes the connection set of the Cayley (di)graph setwise\, this induces a nontrivial graph automorphism that fixes the identity vertex\, which means that the (di)graph is not a DRR or GRR. Checking whether or not there is any group automorphism that fixes a particular connection set can be done very quickly and easily compared with checking whether or not any nontrivial graph automorphism fixes some vertex\, so it would be nice to know if there are circumstances under which the simpler test is enough to guarantee whether or not the Cayley graph is a GRR or DRR. I will present a number of results on this question.\n\n\nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n 
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-5/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20231018T153000
DTEND;TZID=UTC:20231018T163000
DTSTAMP:20260610T222828
CREATED:20231012T115001Z
LAST-MODIFIED:20231012T223528Z
UID:7376-1697643000-1697646600@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Two short talks by grad students Alex Clow and William Kellough. ‘Live’ viewing in Chase 227 for those at Dalhousie. \nTalk 1:\nAlex Clow\, Simon Fraser University\nPolynomially Bounding the Oriented Chromatic Number in Euler Genus \nIn this talk we consider the oriented chromatic number of graphs with bounded Euler genus. In particular\, we present our proofs that the oriented chromatic number is at most $g^{6400}$ for sufficiently large $g$ and at least $\Omega((\frac{g^2}{\log g})^{1/3})$. This is a major improvement over the previous best upper bound which is exponential in genus. We conclude the talk by discussing directions for future study. Joint work with Peter Bradshaw and Jingwei Xu from the University of Illinois at Urbana Champaign. \nTalk 2:\nWilliam Kellough\, Memorial University\nHow to Catch a Cheating Robber on Strong Products \nCops and Robbers is a pursuit-evasion game played on the vertices of a graph. One player controls a set of cops and the other player controls a robber. The cops win if a cop can move to the vertex occupied by the robber in finitely many turns\, otherwise the robber wins. In this talk\, we consider a variation of Cops and Robbers where both players move simultaneously and the robber “cheats” by knowing how the cops will move each round. We will give bounds on the minimum number of cops needed to win this game when played on the strong product of two graphs. This is joint work with Nancy Clarke and Danny Dyer. \nJoin Zoom Meeting\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-4/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
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BEGIN:VEVENT
DTSTART;TZID=UTC:20231004T153000
DTEND;TZID=UTC:20231004T163000
DTSTAMP:20260610T222828
CREATED:20230930T100717Z
LAST-MODIFIED:20230930T100717Z
UID:7351-1696433400-1696437000@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Speaker: Iain Beaton\, Acadia University\nTitle: On the Unimodality of Nearly-Well Dominated Trees\n\n\nAbstract: A polynomial is said to be unimodal if its coefficients are non-decreasing and then non-increasing. The domination polynomial of a graph G is the generating function of the number of dominating sets of each cardinality in G\, and its coefficients have been conjectured to be unimodal. In this talk we will show the domination polynomial of a tree T is unimodal so long as the sizes of the minimal dominating sets of T do not differ by too much. We will also discuss a version of this result for directed trees and its connection to the unimodality conjecture for the independence polynomial of a well-covered tree.\n\n \nZoom link:\n\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-3/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20230920T153000
DTEND;TZID=UTC:20230920T163000
DTSTAMP:20260610T222828
CREATED:20230915T200900Z
LAST-MODIFIED:20230915T200900Z
UID:7306-1695223800-1695227400@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar
DESCRIPTION:Time: 3.30pm\, Atlantic time\, Wednesday Sept.20\nSpeaker: Jessica McDonald\, Auburn University\n\nTitle: On flows (and group-connectivity) in signed graphs \nAbstract:\n\n\n\n\n\n\nIn this talk we’ll start by discussing flows in signed graphs and how it generalizes the usual notion of integer flows in graphs. In particular\, flow-colouring duality of graphs in the plane can be re-interpreted using signed graphs in the projective plane. Also\, where a flow in a graph can be viewed as a sum of flows on cycles\, in a signed graph\, positive cycles and barbells are the key structures to consider. We’ll share a new result\, joint with K. Nurse and A. Brewer-Castano\, about flows in 3-edge-connected signed graphs. In fact\, this result holds for the stronger notion of group-connectivity\, which was introduced as a generalization of flows by Jaeger\, Linial\, Payan\, and Tarsi in 1992. Building on their work and also on work by Li\, Luo\, Ma and Zhang (2018)\, we (mostly) establish a group-connected analog of Seymour’s 6-flow Theorem for signed graphs. \n\n\n\n\n\n\nZoom link:\nhttps://us02web.zoom.us/j/86415230827?pwd=QUxLUnlMdWYzL05zSUJ4bnBCOUJnZz09\n\nMeeting ID: 864 1523 0827\nPasscode: 835547
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-2/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
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BEGIN:VEVENT
DTSTART;TZID=UTC:20230329T153000
DTEND;TZID=UTC:20230329T163000
DTSTAMP:20260610T222828
CREATED:20230325T113759Z
LAST-MODIFIED:20230325T113833Z
UID:7190-1680103800-1680107400@aarms.math.ca
SUMMARY:Atlantic Graph Theory Seminar: Calum MacRury\, University of Toronto
DESCRIPTION:Approximation Schemes for Resource Minimization for Fire Containment\nThe semi-random graph process is an example of an adaptive process for constructing a graph in which random edges are added step by step.  It is adaptive in that there is an online algorithm which has partial control over which random edges are added. Through intelligent decision-making\, the objective of the algorithm is to force the graph to satisfy a fixed graph property with high probability in as few rounds as possible. We first provide upper and lower bounds on the performance of an optimal algorithm when the property corresponds to being Hamiltonian or to containing a perfect matching. This part of the talk is based on joint works with Pawel Pralat and Jane Gao.Afterwards\, we introduce a formal definition of an adaptive random graph process which generalizes both the semi-random graph process\, as well as the Achlioptas process. In this model\, we define a condition called edge-replaceability  which we prove is sufficient for a property to have a sharp threshold. Intuitively\, a property has a sharp threshold if the optimal algorithm’s “success probability” transitions from almost $0$ to almost $1$ in a negligible number of steps.  We apply our result to the semi-random graph process to show that the properties of being Hamiltonian  and of containing a perfect matching each have a sharp threshold. This part of the talk is based on a joint work with Erlang Surya.
URL:https://aarms.math.ca/event/atlantic-graph-theory-seminar-calum-macrury-university-of-toronto/
LOCATION:Online via Zoom
CATEGORIES:AARMS Atlantic Graph Theory Seminar
ORGANIZER;CN="jeannette Janssen":MAILTO:jeannette.janssen@dal.ca
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