中文

Mean Ramsey-Tur\'an numbers

组合数学 2007-05-23 v1

摘要

A ρ\rho-mean coloring of a graph is a coloring of the edges such that the average number of colors incident with each vertex is at most ρ\rho. For a graph HH and for ρ1\rho \geq 1, the {\em mean Ramsey-Tur\'an number} RT(n,H,ρmean)RT(n,H,\rho-mean) is the maximum number of edges a ρ\rho-mean colored graph with nn vertices can have under the condition it does not have a monochromatic copy of HH. It is conjectured that RT(n,Km,2mean)=RT(n,Km,2)RT(n,K_m,2-mean)=RT(n,K_m,2) where RT(n,H,k)RT(n,H,k) is the maximum number of edges a kk edge-colored graph with nn vertices can have under the condition it does not have a monochromatic copy of HH. We prove the conjecture holds for K3K_3. We also prove that RT(n,H,ρmean)RT(n,Kχ(H),ρmean)+o(n2)RT(n,H,\rho-mean) \leq RT(n,K_{\chi(H)},\rho-mean)+o(n^2). This result is tight for graphs HH whose clique number equals their chromatic number. In particular we get that if HH is a 3-chromatic graph having a triangle then RT(n,H,2mean)=RT(n,K3,2mean)+o(n2)=RT(n,K3,2)+o(n2)=0.4n2(1+o(1))RT(n,H,2-mean) = RT(n,K_3,2-mean)+o(n^2)=RT(n,K_3,2)+o(n^2)=0.4n^2(1+o(1)).

关键词

引用

@article{arxiv.math/0408108,
  title  = {Mean Ramsey-Tur\'an numbers},
  author = {Raphael Yuster},
  journal= {arXiv preprint arXiv:math/0408108},
  year   = {2007}
}

备注

9 pages