English

Block colourings of star systems

Combinatorics 2023-03-08 v3

Abstract

An ee-star system of order nn is a decomposition of the complete graph KnK_n into copies of the complete bipartite graph K1,eK_{1,e} (or ee-star). Such systems are known to exist if and only if n2en\geq 2e and ee divides (n2)\binom{n}{2}. We consider block colourings of such systems, where each ee-star is assigned a colour, and two ee-stars which share a vertex receive different colours. We present a computer analysis of block colourings of small 33-star systems. Furthermore, we prove that: (i) for n0,1n\equiv 0,1 mod 2e2e there exists either an nn or (n1)(n-1)-block colourable ee-star system of order nn; and (ii) when e=3e=3, the same result holds in the remaining congruence classes mod 66.

Keywords

Cite

@article{arxiv.2209.04946,
  title  = {Block colourings of star systems},
  author = {Robert F. Bailey and Iren Darijani},
  journal= {arXiv preprint arXiv:2209.04946},
  year   = {2023}
}
R2 v1 2026-06-28T01:05:41.931Z