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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 $\mathbb{F}$ of size at least 4 and any nonsingular matrix $M$ over $\mathbb{F}$ 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 $2^{O(\sqrt{k})}(n + m)$, where $n$ and $m$ denote the numbers of vertices and edges, respectively. This improves the $2^{O(\sqrt{k}\log k)}(n + m)$-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 $\chi(G)$ is at most $f(\omega(G))$ for every $H$-free graph $G$ ("$H$-free" means with no induced subgraph isomorphic to $H$, and $\omega(G)$ 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 $\pm 1$-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 $\pm 1$-assignment converges to a $99\%$-agreement with high …

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Young Researchers in Extremal and Probabilistic Combinatorics

Zoom ID: 554 788 7710 (507464)

The aim of the Young Researchers in Extremal and Probabilistic Combinatorics is to bring together early career researchers working on these topics.  The workshop will consist of several  25 minute talks across three days from October 20 to 22, 2021.  Due to Covid the workshop will be held online. Invited Speakers & Program Oct. 20 …

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

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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, no set can be added to $\mathcal F$ while preserving this property. In 1974, Erdős and Kleitman asked for the smallest possible size of a …

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Martin Milanič, Tree Decompositions with Bounded Independence Number

Zoom ID: 869 4632 6610 (ibsdimag)

The independence number of a tree decomposition $\mathcal{T}$ of a graph is the smallest integer $k$ such that each bag of $\mathcal{T}$ induces a subgraph with independence number at most $k$. If a graph $G$ is given together with a tree decomposition with bounded independence number, then the Maximum Weight Independent Set (MWIS) problem can …

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IBS 이산수학그룹 Discrete Mathematics Group
기초과학연구원 수리및계산과학연구단 이산수학그룹
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IBS Discrete Mathematics Group (DIMAG)
Institute for Basic Science (IBS)
55 Expo-ro Yuseong-gu Daejeon 34126 South Korea
E-mail: dimag@ibs.re.kr, Fax: +82-42-878-9209
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