On June 30, 2020, Dennis Wong from SUNY Korea gave a talk on algorithms to generate Gray codes and universal cycles for weak orders at the Discrete Math Seminar. At the end of the talk, his student, Fabio Calero from SUNY Korea, gave a sketch about another work on Gray codes for ballot sequences. The title of his talk is “Generating Gray codes and universal cycles for weak orders“.

## Jaehoon Kim (김재훈) gave a talk on a resilience version of Pósa’s theorem regarding Hamiltonian cycles at the Discrete Math Seminar

On June 23, 2020, Jaehoon Kim (김재훈) from KAIST presented his work with Padraig Condon, Alberto Espuny Diaz, Daniela Kühn and Deryk Osthus on a resilience version of Pósa’s theorem regarding a sufficient condition on the degree sequence for a graph to have a Hamiltonian cycle at the Discrete Math Seminar. The title of his talk is “A resilience version of Pósa’s theorem“.

## Andreas Holmsen gave a talk on a recent work generalizing the fractional Helly theorem under very weak topological assumptions at the Discrete Math Seminar

On June 16, 2020, Andreas Holmsen from KAIST presented his recent work with Xavier Goaoc and Zuzana Patáková on generalizing the fractional Halley theorem under very weak topological assumptions. The title of his talk was “Fractional Helly and topological complexity“.

## Jiseung Kim (김지승) talked about the hardness and concrete security in cryptography at the Discrete Math Seminar

On June 9, 2020, Jiseung Kim (김지승) from KIAS presented a talk on some aspects of cryptography, including his recent work “Adventures in Crypto Dark Matter: Attacks, Fixes, and Analysis of weak PRF” jointly with Jung Hee Cheon, Wonhee Cho, and Jeong Han Kim. The title of his talk was “Hardness and concrete security in cryptography“.

## Huy-Tung Nguyen gave a talk on the average cut-rank of a graph at the Discrete Math Seminar

On June 2, 2020, Huy-Tung Nguyen from KAIST gave a talk on the graph parameter called the average cut-rank of a graph. The title of his talk is “The average cut-rank of graphs“.

## Hong Liu gave a talk describing approximate structures of an n-vertex m-edge graph minimizing the number of cliques of size k at the Discrete Math Seminar

On May 26, 2020, Hong Liu from University of Warwick presented a talk on his recent work describing approximate structures of an n-vertex m-edge graph minimizing the number of cliques of size k. The title of his talk was “Asymptotic Structure for the Clique Density Theorem”.

## O-joung Kwon (권오정) gave a survey talk on the MIM-width of graphs at the Discrete Math Seminar

On May 19, 2020, O-joung Kwon (권오정) from Incheon National University and IBS Discrete Mathematics Group presented a survey talk on the MIM-width of graphs. The title of his talk was “Mim-width: a width parameter beyond rank-width“.

Note added on June 2020After I presented the talk, Benjamin Bergougnoux commented me that the claim of (Boyaci, Ekim, Shalom 17) at 1:02:40 was recently disproved by Kratochvíl, Masařík, and Novotná (https://arxiv.org/abs/2002.08311). I would like to thank Benjamin for the comment. Whether or not there is a polynomial-time algorithm for Max Cut on proper interval graphs is still open.

## Eun Jung Kim (김은정) gave a talk on the twin-width at the Discrete Math Seminar

On May 12, 2020, Eun Jung Kim (김은정) from LAMSADE, CNRS presented a talk on her recent work on the twin-width. The title of her talk was “Twin-width: tractable FO model checking“. She is visiting the IBS discrete mathematics group from May 12 for about 4 months.

## Due to COVID-19, we decided to postpone two international workshops to be held in August, 2020

Due to COVID-19, it was decided to postpone the following two workshops to be held in August, 2020 at IBS by the organizers of each workshop.

- 2020 IBS Workshop on Extremal and Probabilistic Combinatorics (Initially scheduled on August 24-28, 2020)
- Nonlinear Algebra in Daejeon (Initially scheduled on August 4-13, 2020)

## Seunghun Lee (이승훈) gave a talk on the complexes of subgraphs having no large matching at the Discrete Math Seminar

On April 28, 2020, Seunghun Lee (이승훈) from KAIST presented a talk on the topological property of the non-matching complex, that is a simplicial complex consisting of subgraphs on the same vertex set having no matching of size k and its application to the rainbow matching problem of graphs. The title of his talk is “Leray numbers of complexes of graphs with bounded matching number“.