Cheolwon Heo (허철원), Representations of even-cycle matroids
Room B232 IBS (기초과학연구원)A signed graph is a pair $(G,\Sigma)$ where $G$ is a graph and $\Sigma$ is a subset of edges of $G$. A cycle $C$ of $G$ is a subset of …
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Discrete Math Seminar
Dabeen Lee (이다빈), Mixing sets, submodularity, and chance-constrained optimization
Room B232 IBS (기초과학연구원)A particularly important substructure in modeling joint linear chance-constrained programs with random right-hand sides and finite sample space is the intersection of mixing sets with common binary variables (and possibly …
Kevin Hendrey, Extremal functions for sparse minors
Room B232 IBS (기초과학연구원)The extremal function $c(H)$ of a graph $H$ is the supremum of densities of graphs not containing $H$ as a minor, where the density of a graph is the ratio …
Eunjin Oh (오은진), Feedback Vertex Set on Geometric Intersection Graphs
Room B232 IBS (기초과학연구원)I am going to present an algorithm for computing a feedback vertex set of a unit disk graph of size k, if it exists, which runs in time $2^{O(\sqrt{k})}(n + …
Joonkyung Lee (이준경), Majority dynamics on sparse random graphs
Room B232 IBS (기초과학연구원)Majority dynamics on a graph $G$ is a deterministic process such that every vertex updates its $\pm 1$-assignment according to the majority assignment on its neighbor simultaneously at each step. …
Donggyu Kim (김동규), 𝝘-graphic delta-matroids and their applications
Room B232 IBS (기초과학연구원)Bouchet (1987) defined delta-matroids by relaxing the base exchange axiom of matroids. Oum (2009) introduced a graphic delta-matroid from a pair of a graph and its vertex subset. We define …
Ben Lund, Maximal 3-wise intersecting families
Room B232 IBS (기초과학연구원)A family $\mathcal F$ of subsets of {1,2,…,n} is called maximal k-wise intersecting if every collection of at most k members from $\mathcal F$ has a common element, and moreover, …
Jaehoon Kim (김재훈), 2-complexes with unique embeddings in 3-space
Room B232 IBS (기초과학연구원)A well-known theorem of Whitney states that a 3-connected planar graph admits an essentially unique embedding into the 2-sphere. We prove a 3-dimensional analogue: a simply-connected 2-complex every link graph …
Casey Tompkins, Ramsey numbers of Boolean lattices
Room B232 IBS (기초과학연구원)The poset Ramsey number $R(Q_{m},Q_{n})$ is the smallest integer $N$ such that any blue-red coloring of the elements of the Boolean lattice $Q_{N}$ has a blue induced copy of $Q_{m}$ …
Seonghyuk Im (임성혁), Large clique subdivisions in graphs without small dense subgraphs
Room B232 IBS (기초과학연구원)What is the largest number $f(d)$ where every graph with average degree at least $d$ contains a subdivision of $K_{f(d)}$? Mader asked this question in 1967 and $f(d) = \Theta(\sqrt{d})$ …