On July 27, 2021, Euiwoong Lee (이의웅) from the University of Michigan gave a talk at the Discrete Math Seminar on the proof that the Karger-Stein algorithm finds the minimum k-cuts with the probability $\Omega(n^{-k})$, which is tight and improves previous bounds. The title of his talk was “The Karger-Stein algorithm is optimal for k-cut“.

## Semin Yoo (유세민) gave a talk on an analogue of q-binomial coefficients at the Discrete Math Seminar

On July 20, 2021, Semin Yoo (유세민) from the University of Rochester gave a talk on an analogue of q-binomial coefficients, counting subspaces having the Euclidean quadratic form, and its applications at the Discrete Math Seminar. She will move to KIAS next month as a postdoc. The title of her talk was “Combinatorics of Euclidean spaces over finite fields“.

## Stefan Weltge gave an online talk at the Virtual Discrete Math Colloquium on a strongly polynomial-time algorithm for the integer linear program with bounded subdeterminants and two nonzeros per row

On July 14, 2021, Stefan Weltge from the Technical University of Munich gave an online talk at the Virtual Discrete Math Colloquium on an efficient algorithm to solve the Integer Linear Program defined by an integer matrix whose subdeterminants are bounded by a constant and that contains at most two nonzero entries in each row. The title of his talk was “Integer programs with bounded subdeterminants and two nonzeros per row“.

## Jaehoon Kim (김재훈) gave a talk on the minimum spectral radius of $K_{r+1}$-saturated graphs at the Discrete Math Seminar

On July 13, 2021, Jaehoon Kim (김재훈) from KAIST gave a talk at the Discrete Math Seminar on a lower bound on the spectral radius of a $K_{r+1}$-saturated graph. The title of his talk was “$K_{r+1}$-saturated graphs with small spectral radius“.

## Suil O (오수일) gave a talk on the existence of even and odd [a,b]-factors in h-edge-connected r-regular graphs in terms of eigenvalues at the Discrete Math Seminar

On July 6, 2021, Suil O (오수일) from SUNY Korea gave a talk at the Discrete Math Seminar on upper bounds of certain eigenvalues to guarantee the existence of an even or odd [a,b]-factor in h-edge-connected r-regular graphs. The title of his talk was “Eigenvalues and [a, b]-factors in regular graphs“.

## Florian Gut and Attila Joó gave an online talk on the existence of a large vertex flame in every rooted directed graph of size ℵ_1 at the Virtual Discrete Math Colloquium

On June 30, 2021, Florian Gut and Attila Joó (University of Hamburg) gave an online talk at the Virtual Discrete Math Colloquium on their new result proving that every rooted directed graph of size $\aleph_1$ has a large vertex flame. The title of their talk was “Large vertex-flames in uncountable digraphs“.

## Jeong Ok Choi (최정옥) gave a talk on the non-singularity of some circulant matrices at the Discrete Math Seminar

On June 29, 2021, Jeong Ok Choi (최정옥) from GIST and IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on the non-singularity of some circulant matrices. The title of her talk was “Invertibility of circulant matrices of arbitrary size“.

## Hongseok Yang (양홍석) gave a talk on symmetry-preserving neural networks under DAG-symmetries at the Discrete Math Seminar

On June 22, 2021, Hongseok Yang (양홍석) from KAIST gave a talk at the Discrete Math Seminar on introducing DAG-symmetries and characterizing linear layers of neural networks preserving these symmetries. The title of his talk was “DAG-symmetries and Symmetry-Preserving Neural Networks“.

## Alan Lew gave an online talk on extending the boxicity of graphs to simplicial complexes at the Virtual Discrete Math Colloquium

On June 16, 2021, Alan Lew from the Technion gave an online talk at the Virtual Discrete Math Colloquium on extending a classical theorem of Roberts on an upper bound of the boxicity of graphs to the d-boxicity of simplicial complexes. The title of his talk was “Representability and boxicity of simplicial complexes“.

## O-joung Kwon (권오정) gave a talk on classes of intersection digraphs and their bi-min-width at the Discrete Math Seminar as a part of the “Round the World Relay in Combinatorics”

The “Round the World Relay in Combinatorics” was held from 11 am KST of June 8 to 9 am KST of June 9. O-joung Kwon (권오정) from the Incheon National University and the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar organized as a part of the “Round the World Relay in Combinatorics” at 3 pm KST. His talk was about classes of intersection digraphs and their bi-min-width. The title of his talk was “Classes of intersection digraphs with good algorithmic properties“.