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Eun Jung Kim (김은정), A Constant-factor Approximation for Weighted Bond Cover

Room B232 IBS (기초과학연구원)

The Weighted F-Vertex Deletion for a class F of graphs asks, given a weighted graph G, for a minimum weight vertex set S such that G−S∈F. The case when F is minor-closed and excludes some graph as a minor has received particular attention but a constant-factor approximation remained elusive for Weighted $\mathcal …

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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 a knapsack constraint). In this talk, we first explain basic mixing sets by establishing a strong and previously unrecognized connection to submodularity. In particular, we …

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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 of the number of edges to the number of vertices. Myers and Thomason (2005), Norin, Reed, Thomason and Wood (2020), and Thomason and Wales (2019) …

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Péter Pál Pach, The Alon-Jaeger-Tarsi conjecture via group ring identities

Zoom ID: 869 4632 6610 (ibsdimag)

The Alon-Jaeger-Tarsi conjecture states that for any finite field F of size at least 4 and any nonsingular matrix M over F there exists a vector x such that neither x nor Mx has a 0 component. In joint work with János Nagy we proved this conjecture when the size of the field is sufficiently …

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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 2O(k)(n+m), where n and m denote the numbers of vertices and edges, respectively. This improves the 2O(klog⁡k)(n+m)-time algorithm for this problem on unit disk …

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Paul Seymour, Polynomial bounds for chromatic number

Zoom ID: 869 4632 6610 (ibsdimag)

The Gyárfás-Sumner conjecture says that for every forest H, there is a function f such that the chromatic number χ(G) is at most f(ω(G)) for every H-free graph G ("H-free" means with no induced subgraph isomorphic to H, and ω(G) is the size of the largest clique of G). This well-known conjecture has been proved only for a …

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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 ±1-assignment according to the majority assignment on its neighbor simultaneously at each step. Benjamini, Chan, O'Donnell, Tamuz and Tan conjectured that, in the Erdős-Rényi random graph G(n,p), the random initial ±1-assignment converges to a 99%-agreement with high …

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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 a Γ-graphic delta-matroid for an abelian group Γ, which generalizes a graphic delta-matroid. For an abelian group Γ, a Γ-labelled graph is a graph whose …

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Ben Lund, Maximal 3-wise intersecting families

Room B232 IBS (기초과학연구원)

A family F of subsets of {1,2,…,n} is called maximal k-wise intersecting if every collection of at most k members from F has a common element, and moreover, no set can be added to F while preserving this property. In 1974, Erdős and Kleitman asked for the smallest possible size of a …

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IBS 이산수학그룹 Discrete Mathematics Group
기초과학연구원 수리및계산과학연구단 이산수학그룹
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IBS Discrete Mathematics Group (DIMAG)
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