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“.

## Casey Tompkins gave a talk on the maximum number of edges in 3-uniform hypergraphs without Berge cycles of length 4 at the Discrete Math Seminar

On March 30, 2021, Casey Tompkins from the IBS Discrete Mathematics Group gave a talk at the Discrete Math Seminar on an upper bound for the maximum number of edges in a 3-uniform hypergraph having no Berge cycles of length 4. The title of his talk was “3-uniform hypergraphs avoiding a cycle of length four“.

## Édouard Bonnet gave an online talk on ordered binary structures of bounded twin-width at the Virtual Discrete Math Colloquium

On March 24, 2021, Édouard Bonnet from the LIP, CNRS gave an online talk at the Virtual Discrete Math Colloquium on several characterizations of classes of ordered binary structures of bounded twin-width. The title of his talk was “Twin-width and ordered binary structures“.

## Hong Liu gave a talk on the extremal problem of finding nested cycles with no geometric crossing at the Discrete Math Seminar

On March 22, 2021 at the Discrete Math Seminar, Hong Liu (刘鸿) from the University of Warwick gave a talk on the extremal problem of having nested cycles with no geometric crossing by using the sublinear expanders. The title of his talk was “Nested cycles with no geometric crossing“.

## Yixin Cao gave an online talk on the algorithm for recognizing interval graphs with only four LexBFS searches at the Virtual Discrete Math Colloquium

On March 17, 2021, at the Virtual Discrete Math Colloquium, Yixin Cao (操宜新) from Hong Kong Polytechnic University gave an online talk on the recognition algorithm for interval graphs by using 4 graph searchers with an improved presentation compared to the version of Li and Wu. The title of his talk was “Recognizing (unit) interval graphs by zigzag graph searches“.