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Threshold Functions for Asymmetric Ramsey Properties Involving Cliques
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Contributed Talks of RANDOM
Threshold Functions for Asymmetric Ramsey Properties Involving Cliques
Martin Marciniszyn1 , Jozef Skokan2 , Reto Spöhel1 and Angelika Steger1 
| (1) |
Institute of Theoretical Computer Science, ETH Zurich, 8092 Zurich, Switzerland |
| (2) |
Instituto de Matemática e Estatística, Universidade de São Paulo, 05508-090 São Paulo, SP, Brazil |
Abstract
Consider the following problem: For given graphs G and F1,..., Fk, find a coloring of the edges of G with k colors such that G does not contain Fi in color i. For example, if every Fi is the path P3 on 3 vertices, then we are looking for a proper k-edge-coloring of G, i.e., a coloring of the edges of G with no pair of edges of the same color incident to the same vertex.
Rödl and Ruciński studied this problem for the random graph Gn,p in the symmetric case when k is fixed and F1=...=Fk=F. They proved that such a coloring exists asymptotically almost surely (a.a.s.) provided that p ≤bn–β for some constants b=b(F,k) and β=β(F). Their proof was, however, non-constructive. This result is essentially best possible because for p ≥Bn–β, where B=B(F, k) is a large constant, such an edge-coloring does not exist. For this reason we refer to n–β as a threshold function.
In this paper we address the case when F1,..., Fk are cliques of different sizes and propose an algorithm that a.a.s. finds a valid k-edge-coloring of Gn,p with p ≤ bn–β for some constants b= b( F1,..., Fk, k) and β= β( F1,..., Fk). Kohayakawa and Kreuter conjectured that

is a threshold function in this case. This algorithm can be also adjusted to produce a valid k-coloring in the symmetric case.
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