English

Flip colouring of graphs II

Combinatorics 2025-11-05 v3

Abstract

We give results concerning two problems on the recently introduced \textit{flip colourings of graphs}. For positive integers b,rb, r with b<rb < r, we say that a b+rb + r regular graph is a (b,r)(b,r)-\textit{flip graph} if there exists a red/blue edge colouring such that the red degree of every vertex is rr, the blue degree of every vertex is bb, yet in the closed neighbourhood of every vertex there are more blue edges than red edges. We prove that for integers b,rb, r with 4b<r<b+2b+2624 \leq b < r < b + 2 \left\lfloor\frac{b+2}{6}\right\rfloor^2, small constructions of (b,r)(b,r)-flip graphs on Θ(b+r)\Theta(b+r) vertices are possible. Furthermore, we prove that there exist kk-flip sequences (a1,,ak)(a_1, \dots, a_k) where k>4k > 4, such that aka_k can be arbitrarily large whilst aia_i is constant for 1i<k41 \leq i < \frac{k}{4}.

Keywords

Cite

@article{arxiv.2401.02315,
  title  = {Flip colouring of graphs II},
  author = {Xandru Mifsud},
  journal= {arXiv preprint arXiv:2401.02315},
  year   = {2025}
}

Comments

15 pages, 6 figures. Final journal version; to appear in BICA