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## Discussiones Mathematicae Graph Theory

2005 | 25 | 1-2 | 141-149
Tytuł artykułu

### Two variants of the size Ramsey number

Autorzy
Treść / Zawartość
Warianty tytułu
Języki publikacji
EN
Abstrakty
EN
Given a graph H and an integer r ≥ 2, let G → (H,r) denote the Ramsey property of a graph G, that is, every r-coloring of the edges of G results in a monochromatic copy of H. Further, let $m(G) = max_{F ⊆ G}|E(F)|/|V(F)|$ and define the Ramsey density $m_{inf}(H,r)$ as the infimum of m(G) over all graphs G such that G → (H,r). In the first part of this paper we show that when H is a complete graph Kₖ on k vertices, then $m_{inf}(H,r) = (R-1)/2$, where R = R(k;r) is the classical Ramsey number. As a corollary we derive a new proof of the result credited to Chvatál that the size Ramsey number for Kₖ equals $\binom{R} {2}$. We also study an on-line version of the size Ramsey number, related to the following two-person game: Painter colors on-line the edges provided by Builder, and Painter's goal is to avoid a monochromatic copy of Kₖ. The on-line Ramsey number R̅(k;r) is the smallest number of moves (edges) in which Builder can force Painter to lose if r colors are available. We show that R̅(3;2) = 8 and $R̅(k;2) ≤ 2k\binom{2k-2} {k-1}$, but leave unanswered the question if R̅(k;2) = o(R²(k;2)).
Słowa kluczowe
EN
Kategorie tematyczne
Wydawca
Czasopismo
Rocznik
Tom
Numer
Strony
141-149
Opis fizyczny
Daty
wydano
2005
otrzymano
2003-11-16
Twórcy
autor
• Department of Discrete Mathematics, Adam Mickiewicz University, Poznań, Poland
autor
• Department of Discrete Mathematics, Adam Mickiewicz University, Poznań, Poland
Bibliografia
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•  P. Erdős, R.J. Faudree, C.C. Rousseau and R.H. Schelp, The size Ramsey number, Period. Math. Hungar. 9 (1978) 145-161, doi: 10.1007/BF02018930.
•  E. Friedgut, V. Rödl, A. Ruciński and P. Tetali, Random graphs with a monochromatic triangle in every edge coloring: a sharp threshold, Memoirs of the AMS, to appear.
•  E. Friedgut, Y. Kohayakawa, V. Rödl, A. Ruciński and P. Tetali, Ramsey games against a one-armed bandit, Combinatorics, Probability and Computing 12 (2003) 515-545, doi: 10.1017/S0963548303005881.
•  R.L. Graham, T. Łuczak, V. Rödl and A. Ruciński, Ramsey properties of families of graphs, J. Combin. Theory (B) 86 (2002) 413-419, doi: 10.1006/jctb.2002.2136.
•  J.A. Grytczuk, M. Hałuszczak and H.A. Kierstead, On-line Ramsey Theory, Electr. J. Combin. (Sep 9, 2004), # R57.
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•  A. Kurek, The density of Ramsey graphs (Ph.D. Thesis, AMU, 1997), in Polish.
•  A. Kurek and A. Ruciński, Globally sparse vertex-Ramsey graphs, J. Graph Theory 18 (1994) 73-81.
•  R.D. Luce and H. Raiffa, Games and Decisions (Wiley, 1957).
•  T. Łuczak, A. Ruciński and B. Voigt, Ramsey properties of random graphs, J. Combin. Theory (B) 56 (1992) 55-68, doi: 10.1016/0095-8956(92)90006-J.
•  C. Payan, Graphes equilibres at arboricite rationalle, Europ. J. Combin. 7 (1986) 263-270.
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Typ dokumentu
Bibliografia
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