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BEGIN:VEVENT
DTSTART;TZID=UTC:20250115T153000
DTEND;TZID=UTC:20250115T163000
DTSTAMP:20260611T115125
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:20250122T153000
DTEND;TZID=UTC:20250122T163000
DTSTAMP:20260611T115125
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;VALUE=DATE:20250124
DTEND;VALUE=DATE:20250127
DTSTAMP:20260611T115125
CREATED:20240516T165538Z
LAST-MODIFIED:20240516T165538Z
UID:7619-1737676800-1737935999@aarms.math.ca
SUMMARY:Combinatorial Algebra meets Algebraic Combinatorics 22nd annual workshop
DESCRIPTION:The Combinatorial Algebra meets Algebraic Combinatorics (CAAC) workshop is an annual meeting taking place in Canada since 2004\, with a focus on the continuously evolving interactions between combinatorial algebra and algebraic combinatorics. These meetings provide a strong connection between the two communities and help with the development of these fields. Historically\, the CAAC meetings provided opportunities for graduate students\, postdoctoral fellows\, and early career researchers to present their work\, learn about new research directions in related fields\, and establish future collaborations. The 22nd Annual CAAC conference will take place at the York University from Friday\, January 24\, 2025\, to Sunday\, January 26\, 2025. CAAC 2025 will include four invited 50-minute lectures\, a collection of contributed talks given by graduate students and postdoctoral fellows\, a poster session\, and time for informal social and scientific interactions.
URL:https://aarms.math.ca/event/combinatorial-algebra-meets-algebraic-combinatorics-22nd-annual-workshop/
LOCATION:York University\, 4700 Keele Street\, Toronto\, Ontario\, M3J 1P3\, Canada
CATEGORIES:AARMS sponsored events
ORGANIZER;CN="Sara Faridi":MAILTO:sara.faridi@dal.ca
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20250129T153000
DTEND;TZID=UTC:20250129T163000
DTSTAMP:20260611T115125
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:20250131T120000
DTEND;TZID=UTC:20250131T130000
DTSTAMP:20260611T115125
CREATED:20250127T120717Z
LAST-MODIFIED:20250127T120717Z
UID:7928-1738324800-1738328400@aarms.math.ca
SUMMARY:CRG Seminar: Modelling Fish Stock Biomass Dynamics in a Multi-gear Fishery and Determining the Stock Status
DESCRIPTION:Abstract: A marine fishery is an important sector in many countries as it contributes towards the nutritional requirements of people and provides income and employment to the associated population. Compared to other natural resources fish being a living resource has the capacity for rebuilding through reproduction. Sustainable management of the marine fishery resources is very important to avoid resource depletion as well as collapse. Biomass of individual species needs to be estimated and its dynamics have to be studied regularly for determining vital reference points such as maximum sustainable yield and its use for sustainable management of the fish stocks. An important model used for studying the biomass dynamics of marine fish stocks is the biomass dynamics model and its modified versions. The necessary information required for such study is time series data on fish catch and fishing effort in terms of number of hours of fishing. Most of the fisheries are of multi-species and multi-gear nature with each fishing gear targeting more than one fish species. Hence biomass dynamics models admitting multi-gear type of harvest are most suited for marine fishery management. Annual fish catch along with fishing effort of a group of fishing gears contributing to the catch are simultaneously used in these models to estimate biomass and other model parameters to make conclusions for fisheries management. One of these models applied to the marine fish stocks in India is the focus of this presentation. \nWebex Link: \nJoin from the meeting link \nhttps://mun.webex.com/mun/j.php?MTID=mde5a7b5680e65bb5f262aacc24d5c \n0df \n  \nJoin by meeting number \nMeeting number (access code): 2773 424 0869 \nMeeting password: PdmbjZyU527
URL:https://aarms.math.ca/event/crg-seminar-modelling-fish-stock-biomass-dynamics-in-a-multi-gear-fishery-and-determining-the-stock-status/
LOCATION:online via webex
ORGANIZER;CN="Asokan Mulayath Variyath":MAILTO:variyath@mun.ca
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