BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Leslie Hogben (Iowa State University and and American Institute of
  Mathematics)
DTSTART:20200828T160000Z
DTEND:20200828T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/1/">Zero forcing\, propagation time\, and throttlin
 g on a graph</a>\nby Leslie Hogben (Iowa State University and and American
  Institute of Mathematics) as part of NY Combinatorics Seminar\n\n\nAbstra
 ct\nZero forcing is an iterative process that repeatedly applies a color c
 hange rule to color blue all the vertices of a (simple) graph G\, and the 
 minimum number of initially blue vertices needed to do so is the zero forc
 ing number\, Z(G). The zero forcing number arose as an upper bound for the
  maximum multiplicity of an eigenvalue of matrices having off-diagonal non
 zero pattern described by the edges of the graph and in other applications
 . Variants for positive semidefinite matrices and skew symmetric matrices 
 described by G have also been studied. In addition to determining the zero
  forcing number\, the propagation time (number of rounds needed to color a
 ll vertices blue)\, and throttling (which minimizes a combination of resou
 rces used to accomplish a task and time needed to accomplish it)\, are stu
 died. This talk will give an overview of these related areas.\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sandra Kingan (Brooklyn College\, CUNY)
DTSTART:20200911T160000Z
DTEND:20200911T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/2/">Minor preserving deletable edges in graphs</a>\
 nby Sandra Kingan (Brooklyn College\, CUNY) as part of NY Combinatorics Se
 minar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:No Talk
DTSTART:20200918T160000Z
DTEND:20200918T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/3
DESCRIPTION:by No Talk as part of NY Combinatorics Seminar\n\nAbstract: TB
 A\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Megan Owen (Lehman College\, CUNY)
DTSTART:20200925T160000Z
DTEND:20200925T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/4
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/4/">Two problems on tree-based networks</a>\nby Meg
 an Owen (Lehman College\, CUNY) as part of NY Combinatorics Seminar\n\n\nA
 bstract\nWhen DNA is only passed from parents to offspring\, evolutionary 
 histories can be modelled by a phylogenetic tree. However\, for some organ
 isms\, like bacteria\, the evolutionary process is more complex\, and thei
 r evolutionary history should be modelled with a directed acyclic graph (D
 AG)\, or phylogenetic network. We study two problems on tree-based network
 s\, which are a sub-class of phylogenetic networks built by adding arcs on
 ly between edges of a base tree. Tree-based networks were defined by Franc
 is and Steel to answer the question: how tree-like is evolution? Francis a
 nd Steel showed that determining if a network is tree-based can be decided
  in polynomial time via a reduction to 2SAT. We show that it is NP-hard to
  determine if a network is based on a specific tree by reduction from 3-Di
 mensional Matching (3DM). We also show that a maximum tree covering a phyl
 ogenetic network can be found in polynomial time by reducing the problem t
 o a minimum-cost maximum-flow problem. This is joint work with Katherine S
 t. John (Hunter College) and our Research Experience for Undergraduates (R
 EU) students from Fall 2015 and Fall 2017.\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jo Ellis-Monaghan (University of Amsterdam)
DTSTART:20201002T160000Z
DTEND:20201002T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/5
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/5/">New Dualities From Old: Generating Geometric\, 
 Petrie\, and Wilson Dualities and Trialities of Ribbon Graphs</a>\nby Jo E
 llis-Monaghan (University of Amsterdam) as part of NY Combinatorics Semina
 r\n\n\nAbstract\nWe develop tools to identify and generate new surface emb
 eddings of graphs with various forms of self-duality including geometric d
 uality\, Petrie duality\, Wilson duality\, and both forms of triality (whi
 ch is like duality\, but of order three instead of two). Previous work typ
 ically focused on regular maps (special\, highly symmetric\, embedded grap
 hs)\, but the methods presented here apply to general embedded graphs. In 
 contrast to Wilson's very large self-trial map of type {9\,9}_9 we show th
 at there are self-trial graphs on as few as three edges. We reduce the sea
 rch for graphs with some form of self-duality or self-triality to the stud
 y of one-vertex ribbon graphs. Our results include a fast algorithm that w
 ill find all graphs with any of the various forms of self-duality or self-
 triality in the orbit of a graph that is isomorphic to any twisted dual of
  itself. This is joint work with Lowell Abrams (George Washington Universi
 ty).\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Goedgebeur (Ghent University\, Belgium)
DTSTART:20201009T160000Z
DTEND:20201009T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/6
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/6/">Generation algorithms for solving mathematical 
 and chemical problems</a>\nby Jan Goedgebeur (Ghent University\, Belgium) 
 as part of NY Combinatorics Seminar\n\n\nAbstract\nComputers are often use
 d in combinatorics to determine if combinatorial objects with given struct
 ural or extremal properties exist as these existence problems are often to
 o complex to solve by hand. This is done by designing and implementing gen
 eration algorithms which construct combinatorial objects from a given clas
 s (typically avoiding the generation of isomorphic copies) and analysing t
 he resulting graphs.\n\nIn this talk we will give an introduction to the e
 xhaustive isomorphism-free generation of graphs. We will also give concret
 e examples of how this has helped to gain new insights and solve problems 
 in mathematics and chemistry.\n\nApplications in mathematics include the g
 eneration of cubic graphs and snarks. We will present a new algorithm for 
 the efficient generation of all non-isomorphic cubic graphs and show how t
 his algorithm can be extended to generate snarks efficiently. A snark is a
  cyclically 4-edge-connected cubic graph with chromatic index 4. Snarks ar
 e of interest since for a lot of conjectures it can be proven that if the 
 conjecture is false\, the smallest possible counterexamples will be snarks
 . Our algorithm enabled us to generate all snarks up to 36 vertices\, whic
 h was impossible with previous methods. This new list of snarks allowed us
  to find counterexamples to several published open conjectures.\n\nAn appl
 ication of graph enumeration in chemistry is the generation of the Nobel P
 rize winning fullerenes (cubic plane graphs where all faces are pentagons 
 or hexagons). We will sketch a new algorithm for the generation of all non
 -isomorphic fullerenes. Our implementation of this algorithm allowed us to
  generate all fullerenes up to 400 vertices\, which enabled us to prove th
 at the smallest counterexample to the spiral conjecture has 380 vertices.\
 n\nThis talk is based on joint work with Gunnar Brinkmann (Ghent Universit
 y) and Brendan McKay (Australian National University).\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:David Offner (Carnegie Mellon University)
DTSTART:20201016T160000Z
DTEND:20201016T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/7
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/7/">Path and cycle decompositions of hypercube grap
 hs</a>\nby David Offner (Carnegie Mellon University) as part of NY Combina
 torics Seminar\n\n\nAbstract\nGiven a subgraph H of an n-dimensional hyper
 cube Q_n\, is it possible to partition the edges of the hypercube into edg
 e-disjoint copies of H? The answer is known in certain cases\, such as whe
 n H is a path and n is odd\, and for paths and cycles that are not too lon
 g relative to n when n is even. It is conjectured that a hypercube of even
  dimension can be decomposed into any path satisfying certain necessary di
 visibility conditions. This talk will summarize what is known about edge-d
 ecompositions of the hypercube\, and describe some recent progress toward 
 decomposing hypercubes of even dimension into long paths and cycles. Joint
  work with Maria Axenovich and Casey Tompkins\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ambat Vijayakumar (Cochin University of Science and Technology\, I
 ndia)
DTSTART:20201023T160000Z
DTEND:20201023T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/8
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/8/">Power domination problem - A Survey</a>\nby Amb
 at Vijayakumar (Cochin University of Science and Technology\, India) as pa
 rt of NY Combinatorics Seminar\n\n\nAbstract\nThe notion of power dominati
 on problem in graphs is motivated by the problem of placing Phasor Measure
 ment Units (PMU) in an electric power system. This problem is viewed as a 
 graph theoretic problem by Haynes et al. in 2002. The power domination pro
 blem in graphs consists of finding a minimum set of vertices S that monito
 rs the entire graph following the two "monitoring rules" - domination and 
 propagation rules. The domination rule allows a vertex v in S to monitor i
 tself and all its neighbours. After applying the domination rule on every 
 vertex of S\, if a monitored vertex u has all its neighbours monitored exc
 ept one neighbour w\, then the propagation rule permits the vertex u to mo
 niotor w. If every vertex is monitored after the repeated application of t
 he propagation rule\, we call S a power dominating set (PDS) of G. The min
 imum cardinality of a PDS of G is called the power domination number of th
 e graph. Power domination can be viewed as a variation of domination in wh
 ich there is an additional propagational behaviour of monitored vertices. 
 Later in 2012\, as a generalization of domination and power domination\, C
 hang et al. introduced the notion of k-power domination by adding the poss
 ibility of propagating up to k vertices. In this talk\, we shall give a sh
 ort survey on the power domination problem in graphs\, including the recen
 t works of Seema Varghese and Seethu Varghese.\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Miodrag Iovanov (University of Iowa)
DTSTART:20201030T160000Z
DTEND:20201030T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/9
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/9/">On combinatorial Hopf algebras of multi-complex
 es</a>\nby Miodrag Iovanov (University of Iowa) as part of NY Combinatoric
 s Seminar\n\n\nAbstract\nA fruitful idea in combinatorics is to consider t
 he totality of objects of a certain type\, and encode natural operations o
 n these objects in operations of some algebra with coefficients in a field
  of characteristic 0. We introduce a general class of combinatorial object
 s\, which we call multi-complexes\, which simultaneously generalizes graph
 s\, multigraphs\, hypergraphs and simplicial and delta complexes. We intro
 duce a natural algebra of multi-complexes which is defined as the algebra 
 which has a formal basis C of all isomorphism types of multi-complexes\, a
 nd multiplication is to take the disjoint union. This is a Hopf algebra wi
 th an operation encoding the dissasembly information for such objects\, an
 d extends and generalizes the Hopf algebra of graphs. Such Hopf algebras a
 re connected\, graded commutative and cocommutative\, and by general resul
 ts of Cartier-Kostant-Milnor-Moore\, are just a polynomial algebra. Howeve
 r\, it comes with additional structure which encodes combinatorial informa
 tion\, and the main goal is to describe its structure in a way relating to
  combinatorics. Such structures have been of high interest in literature\,
  both intrinsically and due to applications to combinatorial problems.\n\n
 We give a solution to the problem in this generality and find an explicit 
 basis B of the space of primitives\, and which is of combinatorial relevan
 ce: it is such that each multi-complex is a polynomial with non-negative i
 nteger coefficients of the elements of B\, and each element of B is a poly
 nomial with integer coefficients in C. The coefficients appearing in all t
 hese polynomials are\, up to signs\, numbers counting multiplicities of su
 b-multi-complexes in a multi-complex. Using this\, we also solve the antip
 ode formula problem\, and find the cancellation and grouping free formula 
 for the antipode. Such formulas are usually very difficult to obtain\, and
  constitute a main question for such algebras.\n\nThe main method is to us
 e certain Mobius type formulas for posets of sub-objects of multi-complexe
 s. As examples\, we will explicitly illustrate how our results specialize 
 to the formulas for graphs and simplicial complexes\, or how they speciali
 ze to results in all of the above mentioned particular cases. Time permitt
 ing\, I will show relations to applications of these results to the graph 
 reconstruction conjectures\, and rederiving some results in the literature
  on these questions.\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pawel Rzazewski (Warsaw University of Technology\, Poland)
DTSTART:20201106T170000Z
DTEND:20201106T180000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/10
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/10/">Quasi-polynomial-time algorithms for Independe
 nt Set and related problems in P_t-free graphs</a>\nby Pawel Rzazewski (Wa
 rsaw University of Technology\, Poland) as part of NY Combinatorics Semina
 r\n\n\nAbstract\nThe complexity of the Independent Set problem in P_t-free
  graphs\, i.e.\, graphs that do not contain a path on t vertices as an ind
 uced subgraph\, is one of the main open problems concerning algorithms for
  restricted graph classes. The problem is known to be polynomial-time-solv
 able for t <= 6. Unfortunately the proof is fine-tailored for this class o
 f graphs and our current algorithmic toolbox seems insufficient to provide
  a polynomial-time algorithm for P_t-free graphs\, for every fixed t. In t
 he recent breakthrough\, Gartland and Lokshtanov [FOCS 2020] gave a quasi-
 polynomial-time algorithm for the problem in P_t-free graphs: their algori
 thm runs in time n^O(log^3n)\, where t is assumed to be a constant. Inspir
 ed by their ideas\, Pilipczuk\, Pilipczuk\, and Rzążewski [accepted to S
 OSA 2021] showed an arguably simpler algorithm with an improved running ti
 me bound of n^O(log^2 n).\nDuring the talk I will present the simplified a
 lgorithm and discuss very recent extensions of this approach to different 
 problems\, including 3-Coloring and Feedback Vertex Set.\nJoint work with 
 Peter Gartland\, Daniel Lokshtanov\, Marcin Pilipczuk\, Michał Pilipczuk.
 \n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ortrud Oellermann (University of Winnipeg\, Canada)
DTSTART:20201120T170000Z
DTEND:20201120T180000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/11
DESCRIPTION:by Ortrud Oellermann (University of Winnipeg\, Canada) as part
  of NY Combinatorics Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alejandro Morales (University of Massachusetts\, Amherst)
DTSTART:20201204T170000Z
DTEND:20201204T180000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/12
DESCRIPTION:by Alejandro Morales (University of Massachusetts\, Amherst) a
 s part of NY Combinatorics Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lara Pudwell (Valparaiso University)
DTSTART:20201211T170000Z
DTEND:20201211T180000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/13
DESCRIPTION:by Lara Pudwell (Valparaiso University) as part of NY Combinat
 orics Seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Aparna Lakshmanan S. (Cochin University of Science and Technology\
 , India)
DTSTART:20210903T160000Z
DTEND:20210903T170000Z
DTSTAMP:20260404T111216Z
UID:NewYorkCombinatoricsSeminar/14
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/NewYo
 rkCombinatoricsSeminar/14/">Graph Labeling Problems: From Leech Trees to L
 eech Graphs</a>\nby Aparna Lakshmanan S. (Cochin University of Science and
  Technology\, India) as part of NY Combinatorics Seminar\n\n\nAbstract\nA 
 graph labeling is a function with some specific properties which assigns v
 alues to vertices\, edges\, or both. Graceful labeling\, edge graceful lab
 eling\, and harmonic labeling are some of the well know graph labelings. I
 n this talk\, I will focus on a special kind of edge labeling called Leech
  labeling\, introduced by John Leech in 1975. Let T be a tree of order n. 
 For any edge labeling f from the edge set E to the natural numbers\, the w
 eight of a path P is the sum of the labels of the edges of P and is denote
 d by w(P). If the weights of the $^nC_2$ paths in T are exactly 1\, 2\,...
 \,$^nC_2$\, then f is called a Leech labeling and a tree which admits a Le
 ech labeling is called a Leech tree. I will discuss some known results in 
 Leech labeling\, a new concept called Leech index\, and the possibility of
  extending Leech labeling to general graphs. Some Leech related labeling w
 ill also be discussed. This is joint work with S. Arumugam and Seema Vargh
 ese.\n
LOCATION:https://stable.researchseminars.org/talk/NewYorkCombinatoricsSemi
 nar/14/
END:VEVENT
END:VCALENDAR