English

Coloring graphs with dense neighborhoods

Combinatorics 2012-10-02 v3

Abstract

It is shown that any graph with maximum degree Δ\Delta in which the average degree of the induced subgraph on the set of all neighbors of any vertex exceeds 6k26k2+1Δ+k+6\frac{6k^2}{6k^2 + 1}\Delta + k + 6 is either (Δk)(\Delta - k)-colorable or contains a clique on more than Δ2k\Delta - 2k vertices. In the k=1k=1 case we improve the bound on the average degree to 23Δ+4\frac23\Delta + 4 and the bound on the clique number to Δ1\Delta-1. As corollaries, we show that every graph satisfies χmax{ω,Δ1,4α}\chi \leq \max\set{\omega, \Delta - 1, 4\alpha} and every graph satisfies \chi \leq \max\set{\omega, \Delta - 1, \ceil{\frac{15 + \sqrt{48n + 73}}{4}}}.

Keywords

Cite

@article{arxiv.1209.3646,
  title  = {Coloring graphs with dense neighborhoods},
  author = {Landon Rabern},
  journal= {arXiv preprint arXiv:1209.3646},
  year   = {2012}
}

Comments

Added consequences for independence number and order

R2 v1 2026-06-21T22:06:23.189Z