Tag Archives: András Hajnal

To cheer you up 14: Hong Liu and Richard Montgomery solved the Erdős and Hajnal’s odd cycle problem

Posted on November 17, 2020 by Gil Kalai

The news: In 1981, Paul Erdős and András Hajnal asked whether the sum of the reciprocals of the odd cycle lengths in a graph with infinite chromatic number is necessarily infinite. Hong Liu and Richard Montgomery have just proved that … Continue reading →

Posted in Combinatorics | Tagged , , , , | 7 Comments

The (Random) Matrix and more

Posted on April 21, 2019 by Gil Kalai

Three pictures, and a few related links. Van Vu Spoiler: In one of the most intense scenes, the protagonist, with his bare hands and against all odds, took care of the mighty Wigner semi-circle law in two different ways. (From … Continue reading →

Posted in Combinatorics, People, What is Mathematics | Tagged , , , , , , | 1 Comment