Ramsey multiplicity and the Turán coloring
Advances in Combinatronics (2023)
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Extending an earlier conjecture of Erd\H{o}s, Burr and Rosta conjectured that
among all two-colorings of the edges of a complete graph, the uniformly random
coloring asymptotically minimizes the number of monochromatic copies of any
fixed graph $H$. This conjecture was disproved independently by Sidorenko and
Thomason. The first author later found quantitatively stronger counterexamples,
using the Tur\'an coloring, in which one of the two colors spans a balanced
complete multipartite graph.
We prove that the Tur\'an coloring is extremal for an infinite family of
graphs, and that it is the unique extremal coloring. This yields the first
determination of the Ramsey multiplicity constant of a graph for which the
Burr--Rosta conjecture fails.
We also prove an analogous three-color result. In this case, our result is
conditional on a certain natural conjecture on the behavior of two-color Ramsey
numbers.
Publié le :
@article{ADVC_2023_a5,
author = {Jacob Fox and Yuval Wigderson},
title = {Ramsey multiplicity and the {Tur\'an} coloring},
journal = {Advances in Combinatronics},
publisher = {mathdoc},
year = {2023},
language = {en},
url = {http://geodesic.mathdoc.fr/item/ADVC_2023_a5/}
}
Jacob Fox; Yuval Wigderson. Ramsey multiplicity and the Turán coloring. Advances in Combinatronics (2023). http://geodesic.mathdoc.fr/item/ADVC_2023_a5/