English

Modified vertex Folkman numbers

Combinatorics 2019-03-28 v1

Abstract

Let a1,...,asa_1, ..., a_s be positive integers. For a graph GG the expression Gv(a1,...,as) G \overset{v}{\rightarrow} (a_1, ..., a_s) means that for every coloring of the vertices of GG in ss colors (ss-coloring) there exists i{1,...,s}i \in \{1, ..., s\}, such that there is a monochromatic aia_i-clique of color ii. If mm and pp are positive integers, then Gvmp G \overset{v}{\rightarrow} {m}\big\vert_{p} means that for arbitrary positive integers a1,...,asa_1, ..., a_s (ss is not fixed), such that i=1s(ai1)+1=m\sum_{i = 1}^{s}(a_i - 1) + 1 = m an max{a1,...,as}p\max{\{a_1, ..., a_s\}} \leq p we have Gv(a1,...,as)G \overset{v}{\rightarrow} (a_1, ..., a_s). Let H~(mp;q)={G:Gvmp\mboxandω(G)<q}. \widetilde{\mathcal{H}}({m}\big\vert_{p}; q) = \{G : G \overset{v}{\rightarrow} {m}\big\vert_{p} \mbox{ and } \omega(G) < q\}. The modified vertex Folkman numbers are defined by the equality F~(mp;q)=min{V(G):GH~(mp;q)}. \widetilde{F}({m}\big\vert_{p}; q) = \min{\{|V(G)| : G \in \widetilde{\mathcal{H}}({m}\big\vert_{p}; q)\}}. If qmq \geq m these numbers are known and they are easy to compute. In the case q=m1q = m - 1 we know all of the numbers when p5p \leq 5. In this work we consider the next unknown case p=6p = 6 and we prove with the help of a computer that F~(m6;m1)=m+10. \widetilde{F}({m}\big\vert_{6}; m - 1) = m + 10.

Keywords

Cite

@article{arxiv.1511.02125,
  title  = {Modified vertex Folkman numbers},
  author = {Aleksandar Bikov and Nedyalko Nenov},
  journal= {arXiv preprint arXiv:1511.02125},
  year   = {2019}
}
R2 v1 2026-06-22T11:39:07.219Z