On April 27, 2021, Jungho Ahn (안정호) from KAIST and IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar introducing the well-partitioned chordal graphs and discussing their properties. The title of his talk was “Well-partitioned chordal graphs with the obstruction set and applications“.

## Reinhard Diestel gave an online talk on various applications of the abstract tangle theory at the Virtual Discrete Math Colloquium

On April 21, 2021, Reinhard Diestel from the University of Hamburg gave an online talk at the Virtual Discrete Math Colloquium about the abstract tangle theory and its applications to real-world examples such as clustering. The title of his talk was “Tangles of set separations: a novel clustering method and type recognition in machine learning“.

## Sang-il Oum (엄상일) gave a talk on isotropic systems at the Discrete Math Seminar

On April 20, 2021, Sang-il Oum (엄상일) from the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar introducing isotropic systems introduced by Bouchet in 1980s. The title of his talk was “What is an isotropic system?“.

## István Tomon gave an online talk on semilinear graphs at the Discrete Math Seminar

On April 14, 2021, István Tomon from the ETH Zurich gave an online talk at the Virtual Discrete Math Colloquium on the size of the maximum clique, the size of the maximum independent set, and the chromatic number of a semilinear graph of bounded complexity. The title of his talk was “Ramsey properties of semilinear graphs“.

## William Overman gave a talk on the ordered Ramsey numbers of small graphs at the Discrete Math Seminar

On April 13, 2021, William Overman from the University of California, Irvine and the IBS Discrete Mathematics Group gave a talk on the ordered Ramsey numbers of small graphs at the Discrete Math Seminar. The title of his talk was “Some Ordered Ramsey Numbers of Graphs on Four Vertices“.

## Michał Pilipczuk gave an online talk on the structural properties of powers of graphs in a class of bounded expansion or in a nowhere dense class at the Virtual Discrete Math Colloquium

On April 7, 2021, Michał Pilipczuk from the University of Warsaw gave an online talk at the Virtual Discrete Math Colloquium on the structural properties of powers of graphs in a fixed class of of graphs of bounded expansion or a fixed nowhere-dense class of graphs. The title of his talk was “Structural properties of powers of sparse graphs“.

## Rutger Campbell gave a talk on the hardness of deciding the real representability of complex-representable orientable matroids at the Discrete Math Seminar

On April 6, 2021, Rutger Campbell from the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on the difficulty of deciding whether a matroid given by the independence oracle is representable over the reals even if the matroid is representable over the complex field and is orientable. The title of his talk was “Matroid orientability and representability“.

## Sophie Spirkl gave an online talk on pure pairs in an ordered graph at the Virtual Discrete Math Colloquium

On April 1, 2021, Sophie Spirkl from the University of Waterloo gave an online talk on pure pairs in an ordered graph at the Virtual Discrete Math Colloquium. The title of her talk was “Pure pairs in ordered graphs“.