English

Connected size Ramsey numbers of matchings versus a small path or cycle

Combinatorics 2022-05-10 v1

Abstract

Given two graphs G1,G2G_1, G_2, the connected size Ramsey number r^c(G1,G2){\hat{r}}_c(G_1,G_2) is defined to be the minimum number of edges of a connected graph GG, such that for any red-blue edge colouring of GG, there is either a red copy of G1G_1 or a blue copy of G2G_2. Concentrating on r^c(nK2,G2){\hat{r}}_c(nK_2,G_2) where nK2nK_2 is a matching, we generalise and improve two previous results as follows. Vito, Nabila, Safitri, and Silaban obtained the exact values of r^c(nK2,P3){\hat{r}}_c(nK_2,P_3) for n=2,3,4n=2,3,4. We determine its exact values for all positive integers nn. Rahadjeng, Baskoro, and Assiyatun proved that r^c(nK2,C4)5n1{\hat{r}}_c(nK_2,C_4)\le 5n-1 for n4n\ge 4. We improve the upper bound from 5n15n-1 to (9n1)/2\lfloor (9n-1)/2 \rfloor. In addition, we show a result which has the same flavour and has exact values: r^c(nK2,C3)=4n1{\hat{r}}_c(nK_2,C_3)=4n-1 for all positive integers nn.

Keywords

Cite

@article{arxiv.2205.03965,
  title  = {Connected size Ramsey numbers of matchings versus a small path or cycle},
  author = {Sha Wang and Ruyu Song and Yixin Zhang and Yanbo Zhang},
  journal= {arXiv preprint arXiv:2205.03965},
  year   = {2022}
}

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9 pages