Fractional chromatic number of graphs of bounded maximum degree

Series
Graph Theory Seminar
Time
Tuesday, February 16, 2021 - 3:45pm for 1 hour (actually 50 minutes)
Location
https://us04web.zoom.us/j/77238664391. For password, please email Anton Bernshteyn (bahtoh ~at~ gatech.edu)
Speaker
Zdeněk Dvořák – Charles University – rakdver@iuuk.mff.cuni.czhttps://iuuk.mff.cuni.cz/~rakdver/
Organizer
Anton Bernshteyn

By the well-known theorem of Brooks, every graph of maximum degree Δ ≥ 3 and clique number at most Δ has chromatic number at most Delta. It is natural to ask (and is the subject of a conjecture of Borodin and Kostochka) whether this bound can be improved for graphs of clique number at most Δ - 1. While there has been little progress on this conjecture, there is a number of interesting results on the analogous question for the fractional chromatic number. We will report on some of them, including a result by myself Bernard Lidický and Luke Postle that except for a finite number of counterexamples, every connected subcubic triangle-free graph has fractional chromatic number at most 11/4.