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Ramsey games near the critical threshold
Random Structures and Algorithms ( IF 0.9 ) Pub Date : 2020-10-17 , DOI: 10.1002/rsa.20959 David Conlon 1 , Shagnik Das 2 , Joonkyung Lee 3 , Tamás Mészáros 2
Random Structures and Algorithms ( IF 0.9 ) Pub Date : 2020-10-17 , DOI: 10.1002/rsa.20959 David Conlon 1 , Shagnik Das 2 , Joonkyung Lee 3 , Tamás Mészáros 2
Affiliation
A well‐known result of Rödl and Ruciński states that for any graph H there exists a constant C such that if , then the random graph Gn, p is a.a.s. H‐Ramsey, that is, any 2‐coloring of its edges contains a monochromatic copy of H. Aside from a few simple exceptions, the corresponding 0‐statement also holds, that is, there exists c > 0 such that whenever the random graph Gn, p is a.a.s. not H‐Ramsey. We show that near this threshold, even when Gn, p is not H‐Ramsey, it is often extremely close to being H‐Ramsey. More precisely, we prove that for any constant c > 0 and any strictly 2‐balanced graph H, if , then the random graph Gn, p a.a.s. has the property that every 2‐edge‐coloring without monochromatic copies of H cannot be extended to an H‐free coloring after extra random edges are added. This generalizes a result by Friedgut, Kohayakawa, Rödl, Ruciński, and Tetali, who in 2002 proved the same statement for triangles, and addresses a question raised by those authors. We also extend a result of theirs on the three‐color case and show that these theorems need not hold when H is not strictly 2‐balanced.
中文翻译:
拉姆齐比赛接近临界点
Rödl和Ruciński的著名结果表明,对于任何图H,存在一个常数C,使得如果,则随机图G n, p为aas H- Ramsey,即,其边缘的任何2种颜色都包含a H的单色副本。除了一些简单的例外,相应的0语句也成立,也就是说,存在c > 0,因此只要随机图G n, p都不是H‐ Ramsey。我们证明即使在G n, p不是H‐ Ramsey,通常非常接近H‐ Ramsey。更确切地说,我们证明了对任何恒定ç > 0和任何严格2平衡图表ħ,如果,则该随机图ģ Ñ, p AAS具有这样的特性:每2边着色无单色副本ħ不能延伸到无H着色后添加了额外的随机边缘。这概括了Friedgut,Kohayakawa,Rödl,Ruciński和Tetali的结果,他们在2002年证明了三角形的相同说法,并解决了这些作者提出的问题。我们还在三色情况下扩展了它们的结果,并表明当H并非严格地为2平衡时,这些定理不需要成立。
更新日期:2020-10-30
中文翻译:
拉姆齐比赛接近临界点
Rödl和Ruciński的著名结果表明,对于任何图H,存在一个常数C,使得如果,则随机图G n, p为aas H- Ramsey,即,其边缘的任何2种颜色都包含a H的单色副本。除了一些简单的例外,相应的0语句也成立,也就是说,存在c > 0,因此只要随机图G n, p都不是H‐ Ramsey。我们证明即使在G n, p不是H‐ Ramsey,通常非常接近H‐ Ramsey。更确切地说,我们证明了对任何恒定ç > 0和任何严格2平衡图表ħ,如果,则该随机图ģ Ñ, p AAS具有这样的特性:每2边着色无单色副本ħ不能延伸到无H着色后添加了额外的随机边缘。这概括了Friedgut,Kohayakawa,Rödl,Ruciński和Tetali的结果,他们在2002年证明了三角形的相同说法,并解决了这些作者提出的问题。我们还在三色情况下扩展了它们的结果,并表明当H并非严格地为2平衡时,这些定理不需要成立。