On Some Generalized Vertex Folkman Numbers

نویسندگان

چکیده

For a graph G and integers $$a_i\ge 1$$ , the expression $$G \rightarrow (a_1,\ldots ,a_r)^v$$ means that for any r-coloring of vertices there exists monochromatic $$a_i$$ -clique in some color $$i \in \{1,\ldots ,r\}$$ . The vertex Folkman numbers are defined as $$F_v(a_1,\ldots ,a_r;H) = \min \{|V(G)| : G$$ is H-free ,a_r)^v\}$$ where H graph. Such have been extensively studied $$H=K_s$$ with $$s>\max \{a_i\}_{1\le i \le r}$$ If $$a_i=a$$ all i, then we use notation $$F_v(a^r;H)=F_v(a_1,\ldots ,a_r;H)$$ Let $$J_k$$ be complete $$K_k$$ missing one edge, i.e. $$J_k=K_k-e$$ In this work focus on $$H=J_k$$ particular $$k=4$$ $$a_i\le 3$$ A result by Nešetřil Rödl from 1976 implies $$F_v(3^r;J_4)$$ well $$r\ge 2$$ We present new more direct proof fact. simplest but already intriguing case $$F_v(3,3;J_4)$$ which establish upper bound 135 using $$J_4$$ -free process. obtain exact values bounds few other small cases ,a_r;J_4)$$ when $$a_i $$1 r$$ including $$F_v(2,3;J_4)=14$$ $$F_v(2^4;J_4)=15$$ $$22 F_v(2^5;J_4) 25$$ Note $$F_v(2^r;J_4)$$ smallest number chromatic $$r+1$$ Most results were obtained help computations, graphs found interesting themselves.

برای دانلود باید عضویت طلایی داشته باشید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

On the Vertex Folkman Numbers

For a graph G the symbol G v −→ (a1, . . . , ar) means that in every r-coloring of the vertices of G, for some i ∈ {1, 2, . . . , r}, there exists a monochromatic ai-clique of color i. The vertex Folkman numbers Fv(a1, . . . , ar; q) = min{|V (G)| : G v −→ (a1, . . . , ar) and Kq * G} are considered. We prove that Fv(2, . . . , 2 | {z } r ; r − 1) = r + 7, r ≥ 6 and Fv(2, . . . , 2 | {z } r ; r...

متن کامل

Some remarks on vertex Folkman numbers for hypergraphs

Let F (r,G) be the least order of H such that the clique number of H and G are equal and any r-coloring of the vertices of H yields a monochromatic and induced copy of G. The problem of bounding of F (r,G) was studied by several authors and it is well understood. In this note, we extend those results to uniform hypergraphs.

متن کامل

Chromatic Vertex Folkman Numbers

For graph G and integers a1 ≥ · · · ≥ ar ≥ 2, we write G → (a1, · · · , ar) if and only if for every r-coloring of the vertex set V (G) there exists a monochromatic Kai in G for some color i ∈ {1, · · · , r}. The vertex Folkman number Fv(a1, · · · , ar; s) is defined as the smallest integer n for which there exists a Ks-free graph G of order n such that G→ (a1, · · · , ar). It is well known tha...

متن کامل

New Upper Bound on Vertex Folkman Numbers

In 1970, J. Folkman proved that for a given integer r and a graph G of order n there exists a graph H with the same clique number as G such that every r coloring of vertices of H yields at least one monochromatic copy of G. His proof gives no good bound on the order of graph H, i.e. the order of H is bounded by an iterated power function. A related problem was studied by Luczak, Ruciński and Ur...

متن کامل

Computation of the vertex Folkman numbers

In this note we show that the exact value of the vertex Folkman numbers F (2, 2, 2, 4; 6) and F (2, 3, 4; 6) is 14.

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

ژورنال

عنوان ژورنال: Graphs and Combinatorics

سال: 2023

ISSN: ['1435-5914', '0911-0119']

DOI: https://doi.org/10.1007/s00373-023-02654-8