Ramsey Properties of Random Graphs and Folkman Numbers

For two graphs, G and F, and an integer r ≥ 2 we write G → (F)r if every r-coloring of the edges of G results in a monochromatic copy of F. In 1995, the first two authors established a threshold edge probability for the Ramsey property G(n, p) → (F)r, where G(n, p) is a random graph obtained by incl...

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Main Authors: Rödl Vojtěch, Ruciński Andrzej, Schacht Mathias
Format: Article
Language:English
Published: University of Zielona Góra 2017-08-01
Series:Discussiones Mathematicae Graph Theory
Subjects:
Online Access:https://doi.org/10.7151/dmgt.1971
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author Rödl Vojtěch
Ruciński Andrzej
Schacht Mathias
author_facet Rödl Vojtěch
Ruciński Andrzej
Schacht Mathias
author_sort Rödl Vojtěch
collection DOAJ
description For two graphs, G and F, and an integer r ≥ 2 we write G → (F)r if every r-coloring of the edges of G results in a monochromatic copy of F. In 1995, the first two authors established a threshold edge probability for the Ramsey property G(n, p) → (F)r, where G(n, p) is a random graph obtained by including each edge of the complete graph on n vertices, independently, with probability p. The original proof was based on the regularity lemma of Szemerédi and this led to tower-type dependencies between the involved parameters. Here, for r = 2, we provide a self-contained proof of a quantitative version of the Ramsey threshold theorem with only double exponential dependencies between the constants. As a corollary we obtain a double exponential upper bound on the 2-color Folkman numbers. By a different proof technique, a similar result was obtained independently by Conlon and Gowers.
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spelling doaj.art-41a5df736a0941be8855013b021b6e242023-09-02T16:29:59ZengUniversity of Zielona GóraDiscussiones Mathematicae Graph Theory2083-58922017-08-0137375577610.7151/dmgt.1971dmgt.1971Ramsey Properties of Random Graphs and Folkman NumbersRödl Vojtěch0Ruciński Andrzej1Schacht Mathias2Emory University, Atlanta, United States of AmericaA. Mickiewicz University, Poznań, PolandUniversität Hamburg, Hamburg, GermanyFor two graphs, G and F, and an integer r ≥ 2 we write G → (F)r if every r-coloring of the edges of G results in a monochromatic copy of F. In 1995, the first two authors established a threshold edge probability for the Ramsey property G(n, p) → (F)r, where G(n, p) is a random graph obtained by including each edge of the complete graph on n vertices, independently, with probability p. The original proof was based on the regularity lemma of Szemerédi and this led to tower-type dependencies between the involved parameters. Here, for r = 2, we provide a self-contained proof of a quantitative version of the Ramsey threshold theorem with only double exponential dependencies between the constants. As a corollary we obtain a double exponential upper bound on the 2-color Folkman numbers. By a different proof technique, a similar result was obtained independently by Conlon and Gowers.https://doi.org/10.7151/dmgt.1971ramsey propertyrandom graphfolkman number05c8005c55
spellingShingle Rödl Vojtěch
Ruciński Andrzej
Schacht Mathias
Ramsey Properties of Random Graphs and Folkman Numbers
Discussiones Mathematicae Graph Theory
ramsey property
random graph
folkman number
05c80
05c55
title Ramsey Properties of Random Graphs and Folkman Numbers
title_full Ramsey Properties of Random Graphs and Folkman Numbers
title_fullStr Ramsey Properties of Random Graphs and Folkman Numbers
title_full_unstemmed Ramsey Properties of Random Graphs and Folkman Numbers
title_short Ramsey Properties of Random Graphs and Folkman Numbers
title_sort ramsey properties of random graphs and folkman numbers
topic ramsey property
random graph
folkman number
05c80
05c55
url https://doi.org/10.7151/dmgt.1971
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