English

Ramsey numbers for trees

Combinatorics 2014-10-28 v6

Abstract

For n5n\ge 5 let TnT_n' denote the unique tree on nn vertices with Δ(Tn)=n2\Delta(T_n')=n-2, and let Tn=(V,E)T_n^*=(V,E) be the tree on nn vertices with V={v0,v1,,V=\{v_0,v_1,\ldots, vn1}v_{n-1}\} and E={v0v1,,v0vn3,E=\{v_0v_1,\ldots,v_0v_{n-3}, vn3vn2,vn2vn1}v_{n-3}v_{n-2},v_{n-2}v_{n-1}\}. In this paper we evaluate the Ramsey numbers r(Gm,Tn)r(G_m,T_n') and r(Gm,Tn)r(G_m,T_n^*), where GmG_m is a connected graph of order mm. As examples, for n8n\ge 8 we have r(Tn,Tn)=r(Tn,Tn)=2n5r(T_n',T_n^*)=r(T_n^*,T_n^*)=2n-5, for n>m7n>m\ge 7 we have r(K1,m1,Tn)=m+n3r(K_{1,m-1},T_n^*)=m+n-3 or m+n4m+n-4 according as m1(n3)m-1\mid (n-3) or m1(n3)m-1\nmid (n-3), for m7m\ge 7 and n(m3)2+2n\ge (m-3)^2+2 we have r(Tm,Tn)=m+n3r(T_m^*,T_n^*)=m+n-3 or m+n4m+n-4 according as m1(n3)m-1\mid (n-3) or m1(n3)m-1\nmid (n-3).

Keywords

Cite

@article{arxiv.1103.2685,
  title  = {Ramsey numbers for trees},
  author = {Zhi-Hong Sun},
  journal= {arXiv preprint arXiv:1103.2685},
  year   = {2014}
}

Comments

10 pages

R2 v1 2026-06-21T17:39:13.174Z